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(){
	
	long long int n,a=1;
	std::cin>>n;
	if(n<=20&&n>0){
	while(n!=0){
		a=a*n;
		n--;
	}
	
	std::cout<<a<<std::endl;
}
	return 0;
}