diff --git a/src/int2048.cpp b/src/int2048.cpp
index 0c9c02f..5acc5f8 100644
--- a/src/int2048.cpp
+++ b/src/int2048.cpp
@@ -385,8 +385,7 @@ void int2048::LeftMoveBy(int L) {
   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];
+      this->val[i] += this->val[i - 1] / kPow10[int2048::kNum - small_move];
     }
   }
   this->val[big_move] =
@@ -540,7 +539,9 @@ int2048 operator*(int2048 A, const int2048 &B) {
 
 inline void UnsignedDivide(int2048 &A, const int2048 *pB) {
   int2048 B(*pB);
-  int L1 = A.num_length, L2 = B.num_length;
+  int L1 = (A.num_length + int2048::kNum - 1) / int2048::kNum;
+  int L2 = (B.num_length + int2048::kNum - 1) / int2048::kNum;
+  // L1 and L2 are number of blocks
   /**
    * reference:
    * https://github.com/lzyrapx/Competitive-Programming-Docs/blob/master/WC%E8%AE%B2%E8%AF%BE%E8%B5%84%E6%96%99/%E7%90%86%E6%80%A7%E6%84%89%E6%82%A6%E2%80%94%E2%80%94%E9%AB%98%E7%B2%BE%E5%BA%A6%E6%95%B0%E5%80%BC%E8%AE%A1%E7%AE%97%EF%BC%882012WC%EF%BC%89.pdf
@@ -555,22 +556,37 @@ inline void UnsignedDivide(int2048 &A, const int2048 *pB) {
    * 4. calculate [10^(2*n)/B]*A and ajust
    */
   if (L2 <= 2) {
-    ;
+    long long b = B.val[0] + (long long)B.val[1] * int2048::kStoreBase;
+    __uint128_t c = 0;
+    for (int i = L1 - 1; i >= 0; i--) {
+      c = c * int2048::kStoreBase + A.val[i];
+      A.val[i] = c / b;
+      c %= b;
+    }
+    A.num_length = L1 * int2048::kNum;
+    const static int kPow10[9] = {1,      10,      100,      1000,     10000,
+                                  100000, 1000000, 10000000, 100000000};
+    while (A.num_length > 1 &&
+           A.val[(A.num_length - 1) / int2048::kNum] /
+                   kPow10[(A.num_length - 1) % int2048::kNum] ==
+               0)
+      A.num_length--;
+    return;
   }
   if (2 * L2 < L1) {
     int delta = L1 - 2 * L2;
-    A.LeftMoveBy(delta);
+    A.LeftMoveBy(delta * int2048::kNum);
     L1 += delta;
-    B.LeftMoveBy(delta);
+    B.LeftMoveBy(delta * int2048::kNum);
     L2 += delta;
   }
-  assert(L1 == A.num_length);
-  assert(L2 == B.num_length);
+  assert(L1 == (A.num_length + int2048::kNum - 1) / int2048::kNum);
+  assert(L2 == (B.num_length + int2048::kNum - 1) / int2048::kNum);
   assert(2 * L2 >= L1);
-  int2048 tmp(A);
-  tmp.LeftMoveBy(233);
-  tmp.RightMoveBy(233);
-  assert(tmp == A);
+  int k = 2;
+  do {
+    /* code */
+  } while (k * 2 <= L2);
 }
 int2048 &int2048::Divide(const int2048 &B) {
   if (this == &B) {
diff --git a/tester/cases/3.py b/tester/cases/3.py
index 22f3797..a1f1ffb 100755
--- a/tester/cases/3.py
+++ b/tester/cases/3.py
@@ -36,7 +36,9 @@ opt_python=[]
 
 if True:
   for i in range(0,10):
-    val=randint(-10**100,10**100)
+    val=randint(-10**15,10**15)
+    if i==0:
+      val=randint(-10**100,10**100)
     opt_cpp.append("a_"+str(i)+"=int2048(\""+str(val)+"\");")
     opt_python.append("a_"+str(i)+"="+str(val))
     opt_cpp.append("a_"+str(i)+".print(); puts(\"\");")
@@ -45,8 +47,8 @@ if True:
 if True:
   for i in range(1):
     aid=randint(0,9)
-    bid=randint(0,9)
-    cid=randint(0,9)
+    bid=randint(0,0)
+    cid=randint(1,9)
     op='/'
     bflag="+"
     if randint(0,1)==0:
@@ -80,7 +82,7 @@ for opt in opt_cpp:
   print(opt,file=sourc_cpp)
 print(code_cpp_suf,file=sourc_cpp)
 sourc_cpp.close()
-system("g++ /tmp/3.cpp -I /home/happyzym/CSWorkSpace/Proc/BigHomework/BH-int2048-2023/include/ -L /home/happyzym/CSWorkSpace/Proc/BigHomework/BH-int2048-2023/build/src/ -lint2048 -g -o /tmp/3")
+system("g++ /tmp/3.cpp -I /home/happyzym/CSWorkSpace/Proc/BigHomework/BH-int2048-2023/include/ -L /home/happyzym/CSWorkSpace/Proc/BigHomework/BH-int2048-2023/build/src/ -lint2048 -g -fsanitize=address -o /tmp/3")
 system("/tmp/3 > /tmp/3_cpp.out")
 
 sourc_python=open("/tmp/3.py","w")