int f(int a, int b)
{
	if(a == b) {
		return -1;
	} else {
		int diff = a - b;
		int n = 1;
		int ret = 0;
		while(diff % n == 0) {
			ret = n - 1;
			n *= 2;
		}
		return ret;
	}
}

int calc_b(int* a, int cnt)
{
	int* next = a;
	int ret = 0;
	for(; cnt > 0; cnt--) {
		next++;
		printf("(%d,%d = %d)", *a, *next, f(*a, *next));
		ret ^= f(*a, *next);
	}
	return ret;
}

int main() 
{
	int a[4] = {3,1,2,4};
	printf("%d", a[0]);
	int res_a = a[0];
	for(int i = 1; i < sizeof(a) / sizeof(int); i++) {
		printf("^%d", a[i]);
		res_a ^= a[i];
	}
	printf("=%d\n", res_a);

	int res_b = 0;
	for(int i = 1; i < sizeof(a) / sizeof(int); i++) {
		int b = calc_b(&a[i - 1], sizeof(a) / sizeof(int) - i);
		printf(" b%d = %d\n", i, b);
		res_b ^= b;
	}
	printf("res_b = %d\n", res_b);
	printf("%d^%d=%d\n", res_a, res_b, res_a^res_b);
}