/* 
 * Program to Find Factorial of a Number 
 */

#include <stdio.h>

/* Entry point to program */
int main() 
{
	unsigned int n, i;
	unsigned long fact = 1;
	
	printf("Enter an integer, (max 12): ");
	scanf("%d", &n);
	
	/* Shows error if the user enters a negative integer */
	if (n < 0)
		printf("Error! Factorial of a negative number doesn't exist.");
	else 
	{
		for (i = 1; i <= n; ++i) 
		{
			fact *= i;
		}
		
		printf("Factorial of %d = %lu", n, fact);
	}
	return 0;
}