def solve(a: int, b: int, c: int, d: int) -> int:
    if a == 0 and d < b:
        return b
    elif b == 0 and c < a:
        return a
    elif a == b and c == d and c < a:
        return a + 1
    else:
        return max(a, b)


x: int
y: int
x, y = map(int, input().split())

x2: int
y2: int
x2, y2 = map(int, input().split())

print(solve(x, y, x2, y2))