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 in;
  long long int out=1;
  cin>>in;
  while(in){
    out*=in;
    in--;
  }
  cout<< out<<endl;


}