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,ans = 1;
  cin >>n;
  for(long long int i=1; i<=n; i++) ans*=i;
  cout <<ans<<endl;
  return 0;
}