Write a program which reads an integer n and prints the factorial of n. You can assume that n ≤ 20.



Input

An integer n (1 ≤ n ≤ 20) in a line.

Output

Print the factorial of n in a line.

Example

Input

5


Output

120
#include "bits/stdc++.h"
using namespace std;

int main() {
  long long n,a;
  a=1;
  cin >> n;
  for(int i=0;i<n;i++){
    a=a*(i+1);
  }
  cout << a<<endl;
  return 0;
}

