func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);     int t;     cin >> t;     while (t--) {       int c, d;       cin >> c >> d;       int temp = abs(c - d);       if (temp % 2) {         cout <<  -1  << endl;         continue;       }       if (c == 0 and d == 0) {         cout <<  0  << endl;         continue;       }       if (temp == 0) {         cout <<  1  << endl;         continue;       }       cout <<  2  << endl;     }   }   