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()
{
	int n;
	cin>>n;
	
	long long res=1;
	for(int i=1;i<=n;i++)
		res*=i;
	
	cout<<res<<endl;
	
	return 0;
}