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 main()
{
		int n;
			scanf("%d\n", &n);
				long long m = n;
					while(--n) m *= n;
						printf("%lld\n", m);
							return 0;
}