def fun(x0, y0, x1, y1):
    if x0 == x1 or y0 == y1:
        return 1
    if abs(x1 - x0) + abs(y1 - y0) <= 3:
        return 1
    else:
        return 2


a, b, c, d = map(int, input().split())
print(fun(a, b, c, d))