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 <iostream>
using namespace std;

int main() {
  int n;
  cin >> n;
  long long ans = n;
  while (--n)
    ans *= n;
  cout << ans << endl;
}