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<cstdio>
#include<iostream>
using namespace std;
int main(){
  long long n,a=1;
  cin >> n;
  for(int i=2;i<=n;i++){
    a=a*i;
  }
  cout << a << endl;
}