#include <stdio.h>

#define bool int
#define true 1
#define false 0

bool is_prime ( int num ) {
	int i = num - 1;
	while ( i > 0 ) {
		if ( i != 1 && num % i == 0 )
			return false;
		i--;
	}
	return true;
}

int main ( void ) {
	int numbers[] = {13, 5678889, 7, 100003};
	int i;
	for ( i = 0; i < 4; i++ ) {
		if ( is_prime ( numbers[i] ) )
			printf ( "%d is a prime number.\n", numbers[i] );
		else
			printf ( "%d is not a prime number.\n", numbers[i] );
	}
	return 0;
}