/*
 * Program to compute factorial using loop.
 *
 * (Also checks for overflow.)
 */
#include <stdio.h>
#include <limits.h>
#include <stdlib.h>

int factorial(int n);

int main(void) {
	int n; 
	printf("enter n\n");
	if (scanf("%d", &n) != 1) {
		printf("not number\n");
		return 1;
	}
	if (n < 0) {
		printf("negative\n");
		return 1;
	}
	printf("factorial(%d) is %d\n", n, factorial(n));
	/* uncomment to see maximum int */
	/* printf("maximum int %d\n", INT_MAX); */
	return 0;
}

int factorial(int n) {
	int result = 1;
	for (int i = 1; i <= n; ++i) {
		/* if result * i > INTMAX */
		if (result > (INT_MAX / i)) {
			printf("overflow!\n");
			exit(1);
		}
		result *= i;
	}
	return result;
}