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()
{
  long long int n;
  cin >> n;
  int i = n;
  while(i-- != 1) n *= i;
  cout << n << endl;;
  
}