Untitled

#include <iostream>
using namespace std;

int main() {
    int a, b, c;
    cin >> a >> b;
    if (a > 0 & b < 0 & a % 2 == 0 & b % 2 != 0) {
        c = a - b;
        cout << c;
    } else {
        cout << "NO";
    }
    
    return 0;
}