func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class T1, class T2>   ostream& operator<<(ostream& out, const pair<T1, T2>& p) {     return (out << p.first <<     << p.second << endl);   }   const int INF = 1000000017;   const long long LLINF = 1000000000000000017LL;   const long double inf = 1.0 / 0.0;   const long double eps = 1e-10;   const int MOD = 1e9 + 7;   const int MOD2 = 1e9 + 9;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(nullptr);     int T;     cin >> T;     while (T--) {       int c, d;       cin >> c >> d;       if (c == d) {         if (c == 0) {           cout << 0;         } else {           cout << 1;         }       } else if (abs(c - d) % 2 == 0) {         cout << 2;       } else {         cout << -1;       }       cout <<   n ;     }     return 0;   }   