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 n,b;
	std::cin>>n;
	b=1;
	for(int i=0 ;i<n ; i++)   b *= n -i ;
	std::cout<<b<<endl;
}