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>
int main(){
	int n;
	long long int m=1;
	std::cin>>n;
	for(int i=n;i>0;i--)m*=i;
	std::cout<<m<<std::endl;
	return 0;
}