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<cstdio>

int n;
long long answer=1;

int main()
{
	scanf("%d",&n);
	for(int i=0;i<n;i++)
	{
		answer*=i+1;
	}
	printf("%lld\n",answer);
	return 0;
}