#!/usr/bin/env python3
import sys

def main():
    X, Y = map(int, input().split())
    if X == Y:
        print(0)
        return
    if X == 0:
        print(2)
        return
    if Y == 0:
        print(1)
        return
    print(-1)
    return
   
        
if __name__ == '__main__':
    main()