func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     while (t--) {       int a, b;       cin >> a >> b;       if ((abs(a - b)) % 2) {         cout << -1 << endl;         continue;       }       if (a == b && b == 0) {         cout << 0 << endl;         continue;       }       if (a == b)         cout << 1 << endl;       else         cout << 2 << endl;     }     return 0;   }   