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;

long long fact(long long a){
  if(a<=1)return 1;
  return fact(a-1)*a;
}

int main(){
  int n;
  cin >> n;
  cout << fact(n) << endl;
}