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, res = 1;
  cin >> n;
  for (int i = 1; i <= n; ++i) res *= i;
  cout << res << endl;
}