import numpy as np

x, y = list(map(int, input().split(' ')))
x2, y2 = list(map(int, input().split(' ')))

if x == y and x2 == y2 and np.sign(x) == np.sign(x2) and np.sign(y) == np.sign(y2):
    print(x + 1)
else:
    print(max([x, y]))