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 f(int n){
  if(n==1) return n;
  return n*f(n-1);
}

int main(){

  int n;

  cin>>n;
  cout<<f(n)<<endl;

  return 0;
}