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