x,y = map(int,input().split())
z,w = map(int,input().split())

ans = max(x,y)
if x == y and z == w and abs(x) > abs(z) and x*z > 0:
    ans += 1
if x == -y and z == -w and abs(x) > abs(z) and x*z > 0:
    ans += 1
print(ans)