Untitled

#include <iostream>
using namespace std;

int main()
{
	int n;
	int a;

	cin >> n;
	cin >> a;

	if (n > 0 and a > 0) {
		cout << "NO";
	}
	if (n < 0 and a < 0) {
		cout << "NO";
	}
	if (n > 0 and a < 0) {
		a =-a;
	}
	if (n < 0 and a > 0) {
		n =-n;
	}

	if (n % 2 == 0 and a % 2 == 0) {
		cout << "NO";
		}
	if (n % 2 > 0 and a % 2 > 0) {
		cout << "NO";
	}
	if (n % 2 == 0 and a % 2 > 0) {
		cout << a + n;
	}
	if (n % 2 > 0 and a % 2 == 0) {
		cout << a + n;
	}
}