import math

x1, y1 = map(int, input().split())
x2, y2 = map(int, input().split())
diff = math.fabs(x1 - x2)
clac = lambda x, y: min(math.fabs(x), math.fabs(y))
res = diff + clac(x1, y1)

if diff == 0:
    if math.abs(x2) == math.abs(y2):
        if 0 < x2 < x1 and 0 < y2 < y1:
            res += 1
        elif 0 < x2 < x1 and y1 < y2 < 0:
            res += 1
        elif x1 < x2 < 0 and 0 < y2 < y1:
            res += 1
        elif x1 < x2 < 0 and y1 < y2 < 0:
            res += 1
elif x1 == 0 and x2 == 0:
    if 0 < y2 < y1 or y1 < y2 < 0:
        res += 1
elif y1 == 0 and y2 == 0:
    if 0 < x2 < x1 or x1 < x2 < 0:
        res += 1

print(res)