#include //#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include //using namespace atcoder; using namespace std; using ll = long long; #define all(A) A.begin(),A.end() using vll = vector; #define rep(i, n) for (long long i = 0; i < (long long)(n); i++) using Graph = vector>>>; ll gcd(ll(a), ll(b)) { ll c = a; while (a % b != 0) { c = a % b; a = b; b = c; } return b; } ll N, M, Q; ll an = 0; vll A, B, C, D; void next_combination(vll S){ if (S.size() == N) { ll k = 0; rep(q, Q) { if (S[B[q]] - S[A[q]] == C[q])k += D[q]; } an = max(an, k); //cout << k << endl; } else { vll NE = S; if (S.size() == 0) { for (ll j = 1; j <= M; j++) { NE.push_back(j); next_combination(NE); NE.pop_back(); } } else { for (ll j = S[S.size() - 1]; j <= M; j++) { NE.push_back(j); next_combination(NE); NE.pop_back(); } } } return; } int main(){ ll A, B; cin >> A >> B; ll an = 1e18; for (ll C = 1; C *C <= A + B; C++) { if ((A + B) % C == 0) { if ((B + C) % A == 0 && (A + C) % B == 0) { an = min(an, C); } ll D = (A + B) / C; if ((B + D) % A == 0 && (A + D) % B == 0) { an = min(an, D); } } } if (an <= 1e18-1) { cout << an << endl; } else { cout << -1 << endl; } }