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;
 long long int s=1;
  cin >> n;
  for(int i=0;n-i > 0;i++)
    s=s*(n-i);
  cout << s <<endl;
}