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,i;
  cin >> n;
  long long ans=1;
  for(i=1;i<=n;i++)
  ans*=i;
  cout << ans << endl;
}

