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;
typedef unsigned long long ull;

ull fact(int n){return n>1?n*fact(n-1):1;}
int main(){
	int n;
	cin>>n;
	cout<<fact(n)<<endl;
}