diff --git a/include/int2048.h b/include/int2048.h
index a67ef1d..63fd57a 100644
--- a/include/int2048.h
+++ b/include/int2048.h
@@ -48,7 +48,8 @@ root= 6
 
   __int128_t QuickPow(__int128_t v, long long q);
   void NTTTransform(__int128_t *, int, bool);
-  friend int2048 GetInv(const int2048 &,int);
+  friend int2048 GetInv(const int2048 &, int);
+  void UnsignedMultiplyByInt(int);
 
  public:
   int2048();
@@ -58,7 +59,6 @@ root= 6
   int2048(int2048 &&) noexcept;
   ~int2048();
 
-  void UnsignedMultiplyByInt(int);
   void LeftMoveBy(int);
   void RightMoveBy(int);
 
diff --git a/tester/proc.cpp b/tester/proc.cpp
index 8713d06..09efbd0 100644
--- a/tester/proc.cpp
+++ b/tester/proc.cpp
@@ -4,7 +4,7 @@ int main()
   using namespace sjtu;
   int2048 a("1234567871928347194791784918734981");
   a.print(); puts("");
-  a.UnsignedMultiplyByInt(2147483647);
+  // a.UnsignedMultiplyByInt(2147483647);
   a.print(); puts("");
   return 0;
 }
\ No newline at end of file