import sys
input=sys.stdin.readline
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))
mod=10**9+7

def main():
    A,B=MI()
    if B==0:
        print(1)
    elif A==-1:
        print(2)
    else:
        print(-1)
    


main()