Wilsons Theorem :: Stupid Integers.

wilson.c

// There is something not right here... 

#include <stdio.h>

long f(int x);

int main(void){
	int p;
	printf("WILSONS THEORM for PRIME NUMBERS\nPlease enter a number: ");
	scanf("%d", &p);
	int ans = (f(p - 1) + 1) % p;
	if(ans == 0) printf("%d IS a prime number!: ( %d - 1 )! + 1 mod ( %d == 0)\n", p, p, p);
	else printf("%d is NOT a prime number!\n", p);
}

long f(int x){
	int i, ret = 1;
	for(i = 1; i <= x; i++) ret *= i;
	return ret;
}