/* 证明歌德巴赫猜想 */
#include <stdio.h>
#include <math.h>

int input_data(void) {
	int data = 0;

	do {
		printf("Please input a even integer (>=6):");
		scanf("%d", &data);
	} while (data < 6 || data % 2 == 1);

	return data;
}

int is_prime(const int data) {
	int i = 0;
	int max = sqrt(data);

	for (i = 2; i <= max; ++i) {
		if (data % i == 0)
			return -1;
	}

	return 0;
}

int goldbach_conjecture(const int n) {
	int a = 0;
	int mid = n / 2;

	for (a = 3; a <= mid; a += 2) {
		if (0 == is_prime(a)) {
			if (0 == is_prime(n - a)) {
				printf("%d can be devided into two prime number: %d and %d\n",
						n, a, n - a);
				return 0;
			}
		}
	}

	return -1;
}

int main(void) {
	int n = 0;
	int flag = 0;

	/* 输入一个正整数 */
	n = input_data();

	/* 证明猜想 */
	flag = goldbach_conjecture(n);
	if (0 == flag) {
		printf("The Goldbach's conjecture is correct!\n");
	} else {
		printf("The Goldbach's conjecture is wrong!\n");
	}

	return 0;
}