diff --git a/include/int2048.h b/include/int2048.h
index 402e249..ce94023 100644
--- a/include/int2048.h
+++ b/include/int2048.h
@@ -15,7 +15,7 @@ class int2048 {
    * num_length is the length of the integer, (num_length+kNum-1)/kNum is the
    * length of val with data. Note that position in val without data is 0.
    */
-  const static int kMod = 100000000, kNum = 8, kDefaultLength = 10;
+  const static int kStoreBase = 100000000, kNum = 8, kDefaultLength = 10;
   const static int kMemAdditionScalar = 2, kMemDeleteScalar = 4;
   /**
    * the follow data used by NTT is generated by this code:
@@ -50,7 +50,8 @@ root= 6
   void NTTTransform(__int128_t *, int, bool);
 
   void RightMoveBy(int);
-
+  void ProcessHalfBlock();
+  void RestoreHalfBlock();
  public:
   int2048();
   int2048(long long);
diff --git a/src/int2048.cpp b/src/int2048.cpp
index f2b1a42..17a9bf4 100644
--- a/src/int2048.cpp
+++ b/src/int2048.cpp
@@ -186,8 +186,8 @@ inline void UnsignedAdd(int2048 &A, const int2048 *const pB,
          i++) {
       if (i < (pB->num_length + int2048::kNum - 1) / int2048::kNum)
         A.val[i] += pB->val[i];
-      if (i + 1 < A.buf_length) A.val[i + 1] += A.val[i] / int2048::kMod;
-      A.val[i] %= int2048::kMod;
+      if (i + 1 < A.buf_length) A.val[i + 1] += A.val[i] / int2048::kStoreBase;
+      A.val[i] %= int2048::kStoreBase;
     }
   } else {
     for (int i = (std::max(A.num_length, pB->num_length) + int2048::kNum - 1) /
@@ -196,9 +196,9 @@ inline void UnsignedAdd(int2048 &A, const int2048 *const pB,
          i >= 0; i--) {
       if (i < (pB->num_length + int2048::kNum - 1) / int2048::kNum)
         A.val[i] += pB->val[i];
-      if (A.val[i] >= int2048::kMod && i - 1 >= 0) {
-        A.val[i - 1] += A.val[i] / int2048::kMod;
-        A.val[i] %= int2048::kMod;
+      if (A.val[i] >= int2048::kStoreBase && i - 1 >= 0) {
+        A.val[i - 1] += A.val[i] / int2048::kStoreBase;
+        A.val[i] %= int2048::kStoreBase;
       }
     }
   }
@@ -261,20 +261,22 @@ inline void UnsignedMinus(int2048 &A, const int2048 *const pB, bool inverse) {
          i++) {
       A.val[i] -= pB->val[i];
       if (A.val[i] < 0 && i + 1 < A.buf_length) {
-        A.val[i] += int2048::kMod;
+        A.val[i] += int2048::kStoreBase;
         A.val[i + 1]--;
       }
     }
   } else {
     int blocks_A = (A.num_length + int2048::kNum - 1) / int2048::kNum;
     int blocks_B = (pB->num_length + int2048::kNum - 1) / int2048::kNum;
-    if (blocks_A < blocks_B) A.ClaimMem(blocks_A * int2048::kNum);
-    blocks_A = (A.num_length + int2048::kNum - 1) / int2048::kNum;
+    if (blocks_A < blocks_B) {
+      A.ClaimMem(blocks_B * int2048::kNum);
+      blocks_A = blocks_B;
+    }
     for (int i = (pB->num_length + int2048::kNum - 1) / int2048::kNum - 1;
          i >= 0; i--) {
       if (i < blocks_B && i < blocks_A) A.val[i] -= pB->val[i];
       if (i < blocks_A && A.val[i] < 0 && i - 1 >= 0) {
-        A.val[i] += int2048::kMod;
+        A.val[i] += int2048::kStoreBase;
         A.val[i - 1]--;
       }
     }
@@ -394,6 +396,63 @@ __int128_t int2048::QuickPow(__int128_t v, long long q) {
   }
   return ret;
 }
+
+// /**
+//  * @brief Move the number to the left by L digits. That is, v'=v*(10^L)
+//  */
+// void int2048::LeftMoveBy(int L) {
+//   const static int kPow10[9] = {1,      10,      100,      1000,     10000,
+//                                 100000, 1000000, 10000000, 100000000};
+//   int big_move = L / int2048::kNum;
+//   int small_move = L % int2048::kNum;
+//   this->ClaimMem(this->num_length + L);
+//   for (int i = this->buf_length - 1; i >= big_move; i--) {
+//     this->val[i] = this->val[i - big_move];
+//   }
+//   for (int i = 0; i < big_move; i++) {
+//     this->val[i] = 0;
+//   }
+//   this->num_length += big_move * int2048::kNum;
+//   if (small_move == 0) return;
+//   for (int i = this->buf_length - 1; i >= 0; i--) {
+//     (this->val[i] *= kPow10[small_move]) %= int2048::kStoreBase;
+//     if (i - 1 >= 0) {
+//       this->val[i] += this->val[i - 1] / kPow10[int2048::kNum - small_move];
+//     }
+//   }
+// }
+
+/**
+ * @brief Move the number to the right by L digits. That is, v'=v//(10^L)
+ */
+void int2048::RightMoveBy(int L) {
+  if (L >= this->num_length) {
+    this->num_length = 1;
+    this->val[0] = 0;
+    return;
+  }
+  int big_move = L / int2048::kNum;
+  int small_move = L % int2048::kNum;
+  for (int i = 0; i < this->buf_length - big_move; i++) {
+    this->val[i] = this->val[i + big_move];
+  }
+  for (int i = this->buf_length - big_move; i < this->buf_length; i++) {
+    this->val[i] = 0;
+  }
+  this->num_length -= big_move * int2048::kNum;
+  if (small_move == 0) return;
+  const static int kPow10[9] = {1,      10,      100,      1000,     10000,
+                                100000, 1000000, 10000000, 100000000};
+  for (int i = 0; i < this->buf_length; i++) {
+    this->val[i] /= kPow10[small_move];
+    if (i + 1 < this->buf_length) {
+      this->val[i] += this->val[i + 1] % kPow10[small_move] *
+                      kPow10[int2048::kNum - small_move];
+    }
+  }
+  this->num_length -= small_move;
+}
+
 void int2048::NTTTransform(__int128_t *a, int NTT_blocks,
                            bool inverse = false) {
   for (int i = 1, j = 0; i < NTT_blocks; i++) {
@@ -434,13 +493,26 @@ inline void UnsignedMultiply(int2048 &A, const int2048 *pB,
   __int128_t *pDA = new __int128_t[NTT_blocks]();
   __int128_t *pDB = new __int128_t[NTT_blocks]();
   __int128_t *pDC = new __int128_t[NTT_blocks]();
-  for (int i = 0; i < blocks_of_A; i++) {
-    pDA[i << 1] = A.val[i] % int2048::kNTTBlockBase;
-    pDA[(i << 1) | 1] = A.val[i] / int2048::kNTTBlockBase;
-  }
-  for (int i = 0; i < blocks_of_B; i++) {
-    pDB[i << 1] = pB->val[i] % int2048::kNTTBlockBase;
-    pDB[(i << 1) | 1] = pB->val[i] / int2048::kNTTBlockBase;
+  if (!inverse) {
+    for (int i = 0; i < blocks_of_A; i++) {
+      pDA[i << 1] = A.val[i] % int2048::kNTTBlockBase;
+      pDA[(i << 1) | 1] = A.val[i] / int2048::kNTTBlockBase;
+    }
+    for (int i = 0; i < blocks_of_B; i++) {
+      pDB[i << 1] = pB->val[i] % int2048::kNTTBlockBase;
+      pDB[(i << 1) | 1] = pB->val[i] / int2048::kNTTBlockBase;
+    }
+  } else {
+    pDA[0] = A.val[0];
+    for (int i = 1; i < blocks_of_A; i++) {
+      pDA[i << 1] = A.val[i] % int2048::kNTTBlockBase;
+      pDA[(i << 1) - 1] = A.val[i] / int2048::kNTTBlockBase;
+    }
+    pDB[0] = pB->val[0];
+    for (int i = 1; i < blocks_of_B; i++) {
+      pDB[i << 1] = pB->val[i] % int2048::kNTTBlockBase;
+      pDB[(i << 1) - 1] = pB->val[i] / int2048::kNTTBlockBase;
+    }
   }
   A.NTTTransform(pDA, NTT_blocks);
   A.NTTTransform(pDB, NTT_blocks);
@@ -465,8 +537,15 @@ inline void UnsignedMultiply(int2048 &A, const int2048 *pB,
   int flag_store = A.flag;
   A.ClaimMem(NTT_blocks * 4);
   memset(A.val, 0, A.buf_length * sizeof(int));
-  for (int i = 0; i < NTT_blocks / 2; i++) {
-    A.val[i] = pDC[(i << 1) | 1] * int2048::kNTTBlockBase + pDC[i << 1];
+  if (!inverse) {
+    for (int i = 0; i < NTT_blocks / 2; i++) {
+      A.val[i] = pDC[(i << 1) | 1] * int2048::kNTTBlockBase + pDC[i << 1];
+    }
+  } else {
+    A.val[0] = pDC[0];
+    for (int i = 1; i < NTT_blocks / 2; i++) {
+      A.val[i] = pDC[(i << 1) - 1] * int2048::kNTTBlockBase + pDC[i << 1];
+    }
   }
   A.num_length = NTT_blocks * 4;
   const static int kPow10[9] = {1,      10,      100,      1000,     10000,
@@ -516,35 +595,24 @@ int2048 operator*(int2048 A, const int2048 &B) {
   A.Multiply(B);
   return std::move(A);
 }
-
-void int2048::RightMoveBy(int L) {
-  if (L >= this->num_length) {
-    this->num_length = 1;
-    this->val[0] = 0;
-    return;
+void int2048::ProcessHalfBlock() {
+  this->ClaimMem(this->num_length + int2048::kNTTBlockBase);
+  int blocks_num = (this->num_length + int2048::kNum - 1) / int2048::kNum;
+  for (int i = blocks_num - 1; i >= 1; i--) {
+    val[i] /= int2048::kNTTBlockBase;
+    val[i] += (val[i - 1] % int2048::kNTTBlockBase) * int2048::kNTTBlockBase;
   }
-  int big_move = L / int2048::kNum;
-  int small_move = L % int2048::kNum;
-  for (int i = 0; i < this->buf_length - big_move; i++) {
-    this->val[i] = this->val[i + big_move];
-  }
-  for (int i = this->buf_length - big_move; i < this->buf_length; i++) {
-    this->val[i] = 0;
-  }
-  this->num_length -= big_move * int2048::kNum;
-  if (small_move == 0) return;
-  const static int kPow10[9] = {1,      10,      100,      1000,     10000,
-                                100000, 1000000, 10000000, 100000000};
-  for (int i = 0; i < this->buf_length; i++) {
-    this->val[i] /= kPow10[small_move];
-    if (i + 1 < this->buf_length) {
-      this->val[i] += this->val[i + 1] % kPow10[small_move] *
-                      kPow10[int2048::kNum - small_move];
-    }
-  }
-  this->num_length -= small_move;
+  val[0] /= int2048::kNTTBlockBase;
+}
+void int2048::RestoreHalfBlock() {
+  int blocks_num = (this->num_length + int2048::kNum - 1) / int2048::kNum;
+  for (int i = 0; i < blocks_num - 1; i++) {
+    val[i] *= int2048::kNTTBlockBase;
+    val[i] %= int2048::kStoreBase;
+    val[i] += val[i + 1] / int2048::kNTTBlockBase;
+  }
+  (val[blocks_num - 1] *= int2048::kNTTBlockBase) %= int2048::kStoreBase;
 }
-
 inline void UnsignedDivide(int2048 &A, const int2048 *pB) {
   int L1 = A.num_length, L2 = pB->num_length;
   if (&A == pB) throw "UnsignedDivide: A and B are the same object";
@@ -572,8 +640,10 @@ inline void UnsignedDivide(int2048 &A, const int2048 *pB) {
   int2048 inverse_B(*pB);
   for (int i = 0; (i << 1) < (pow_B + 1); i++)
     std::swap(inverse_B.val[i], inverse_B.val[pow_B - i]);
-  int2048 x(int2048::kMod);
-  assert(x.val[1] == 1);
+  int2048 x(
+      int2048::kStoreBase *
+      (long long)std::max(1, int2048::kStoreBase / (inverse_B.val[0] + 1)));
+  assert(x.val[1] == std::max(1, int2048::kStoreBase / (inverse_B.val[0] + 1)));
   int *store[2];
   store[0] = new int[pow_A + 5]();
   store[1] = new int[pow_A + 5]();
@@ -582,11 +652,41 @@ inline void UnsignedDivide(int2048 &A, const int2048 *pB) {
     store[0][i] = A.val[i];
     store[1][i] = -1;
   }
+  int inverseB_error = 0;
+  if (inverse_B.val[0] >= int2048::kNTTBlockBase) {
+    inverseB_error = 1;
+    inverse_B.ProcessHalfBlock();
+  }
   while (true) {
-    int2048 invsere_two(2), tmp_x(x);
+    int2048 inverse_two(2), tmp_x(x);
+    int tmp_x_error = 0;
+    if (tmp_x.val[0] >= int2048::kNTTBlockBase) {
+      tmp_x_error = 1;
+      tmp_x.ProcessHalfBlock();
+    }
     UnsignedMultiply(tmp_x, &inverse_B, true);
-    UnsignedMinus(invsere_two, &tmp_x, true);
-    UnsignedMultiply(x, &invsere_two, true);
+    tmp_x.num_length =
+        ((tmp_x.num_length + int2048::kNum - 1) / int2048::kNum) *
+        int2048::kNum;
+    for (int i = 0; i < tmp_x_error + inverseB_error; i++)
+      tmp_x.RestoreHalfBlock();
+    UnsignedMinus(inverse_two, &tmp_x, true);
+    inverse_two.num_length =
+        ((inverse_two.num_length + int2048::kNum - 1) / int2048::kNum) *
+        int2048::kNum;
+    int inverse_two_error = 0, x_error = 0;
+    if (inverse_two.val[0] >= int2048::kNTTBlockBase) {
+      inverse_two_error = 1;
+      inverse_two.ProcessHalfBlock();
+    }
+    if (x.val[0] >= int2048::kNTTBlockBase) {
+      x_error = 1;
+      x.ProcessHalfBlock();
+    }
+    UnsignedMultiply(x, &inverse_two, true);
+    x.num_length =
+        ((x.num_length + int2048::kNum - 1) / int2048::kNum) * int2048::kNum;
+    for (int i = 0; i < x_error + inverse_two_error; i++) x.RestoreHalfBlock();
     /**
      * now x is the next x, store[tot] stores last x, store[tot^1] stores the x
      * previous to store[x]
@@ -617,6 +717,9 @@ inline void UnsignedDivide(int2048 &A, const int2048 *pB) {
       else
         store[tot][i] = 0;
     }
+    fprintf(stderr, "x: ");
+    for (int i = 0; i < blocks_of_x; i++) fprintf(stderr, "%08d ", x.val[i]);
+    fprintf(stderr, "\n");
   }
   delete[] store[0];
   delete[] store[1];