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()
{
    int n;
    cin >> n;
    cout << (long long)tgamma(n + 1) << endl;
    return 0;
}