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(){
   int i,n;
   long long int r;
  r=1;
  cin>>n;
  for(i=1;i<=n;++i){
    r=r*i;
  }
 cout<<r<<endl;
}