#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; const double PI = 3.14159265358979323846; const double EPS = 1e-12; const int INF = 1<<25; typedef pair P; typedef long long ll; typedef unsigned long long ull; int main(){ ll a, b; cin>>a>>b; ll res = -2; if(a