def keiro(goal, fu):
    if fu == [0, 0]:
        x, y = goal[0], goal[1]
        if x > y:
            x, y = y, x
        ans = x + (y - x)
        return ans
    if (goal[0] == goal[1]) and (fu[0] == fu[1]) and (fu[0] < goal[0]):
        ans = keiro(goal, [0, 0]) + 1
        return ans
    else:
        ans = keiro(goal, [0, 0])
        return ans

def main():
    x, y = map(int, input().split())
    goal = [x, y]
    x1, y1 = map(int, input().split())
    fu = [x1, y1]
    print(keiro(goal, fu))

if __name__ == '__main__':
    main()