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

def sign(x):
    return (x > 0) - (x < 0)

s = min(abs(x), abs(y))
l = max(abs(x), abs(y))
ans = s + l - s

if sign(x) == sign(x2) and sign(y) == sign(y2):
    if abs(x) == abs(y) and abs(x2) == abs(y2):
        if abs(x) > abs(x2):
            ans += 1
print(ans)