import math
from math import sqrt
import sys
from collections import deque, defaultdict
from heapq import heappop, heappush
from copy import deepcopy

INF=10**18
MOD=10**9+7
MAX=10**5+7

#N,K=map(int, input().split())
#A=list(map(int, input().split()))

def main():
  A,B=map(int, input().split())

  if B==0: print(1)
  elif A==-1: print(2)
  else: print(-1)



if __name__ == '__main__':
    main()