def main():
    a, b, c, d = map(int, input().split())
    x = abs(a-c)
    y = abs(b-d)
    if x == 0 and y == 0:
        print(0)
    elif x == 0 or y == 0 or (2 >= x and 2 >= y and (x != 2 or y != 2)):
        print(1)
    else:
        print(2)
    pass


if __name__ == "__main__":
    main()