#include <bits/stdc++.h>   using namespace std;   int main() {     unsigned long long A, B;     cin >> A >> B;     if (A < B) {       puts( -1 );       return 0;     }     if ((A - B) % 2 != 0) {       puts( -1 );       return 0;     }     unsigned long long C = (A - B) / 2;     unsigned long long X = 0, Y = 0;     for (unsigned long long bit = 1ULL << 63; bit >= 1; bit >>= 1) {       bool dif = (B & bit);       bool allHas = (C & bit);       if (allHas && dif) {         puts( -1 );         return 0;       }       if (allHas) {         X |= bit;         Y |= bit;       }       if (dif) {         Y |= bit;       }     }     cout << X <<     << Y << endl;   }   