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
//14
#include<iostream>

using namespace std;

int main(){
  int n;
  long long ans=1;
  cin>>n;
  while(n){
    ans*=n--;
  }
  cout<<ans<<endl;
  return 0;
}