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 f=1;
  int i;

  cin >> i;

  for(; i>1; i--){
      f*=i;
  }

  cout << f << "\n";

  return 0;
}