r1, c1, r2, c2 = map(int, input().split())

r = r2 - r1
c = c2 - c1

if (r, c) == (0, 0):
    ans = 0
elif r == c or r == -c: 
    ans = 1
elif abs(r) + abs(c) <= 3:
    ans = 1
elif (r ^ c ^ 1) & 1:
    ans = 2
elif abs(r) + abs(c) <= 6:
    ans = 2
elif abs(r + c) <= 3 or abs(r - c) <= 3:
    ans = 2
else:
    ans = 3

print(ans)