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 int ans = 1;
 for(int i=1; i<=n; i++) ans *= i;

 cout << ans << '\n';

 return 0;
}