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 a[21],b;
  a[1]=1;
  for(int i=2;i<=20;i++)a[i]=a[i-1]*i;
  cin>>b;
  cout<<a[b]<< endl;
  return 0;
}