蛙声一片

#include <bits/stdc++.h>
using namespace std;
const int N = 5010;
int a[N], b[N];
int len = 1, len2 = 1;
inline void add()
{
  
}
inline int mul(int x[], int y)
{
  for (int i = 1; i <= len; i++)
  {
    x[i] *= y;
  }
  for (int i = 1; i < len; i++)
  {
    x[i+1] += x[i] / 10;
    x[i] %= 10;
  }
  while (x[len] >= 10)
  {
    x[len+1] += x[len] / 10;
    x[len] %= 10;
    len++;
  }
  return len;
}
int main()
{
  int n;
  scanf("%d", &n);
  b[1] = 1;
  for (int i = 1; i <= n; i++)
  {
    mul(b, i);
    add();
  }
  for (int i = len2; i >= 1; i--)
  {
    printf("%d", a[i]);
  }
  return 0;
}