/* Let the user type in a number n.  Then output n!. */
#include <stdio.h>
#include <stdlib.h>

long factorial(long n);

int main()
{
	long n;

	printf("Please type in a number and press RETURN.\n");
	scanf("%ld", &n);

	printf("%ld\n", factorial(n));
	return EXIT_SUCCESS;
}

/* Return n!. */

#if 0
long factorial(long n)
{
	long i;
	long product = 1;

	for (i = 1; i <= n ++i) {		/* Why not start at zero? */
		product *= i;
	}
	return product;
}
#endif

#if 0
long factorial(long n)
{
	if (n <= 1) {
		return 1;
	}

	return n * factorial(n - 1);
}
#endif

long factorial(long n)
{
	return n <= 1 ? 1 : n * factorial(n - 1);
}