def do():
    a,b, c,d = map(int, input().split())
    if a==c and b==d:
        print(0)
        return 
    if a==c or b == d:
        print(1)
        return
    if (abs(a-c) + abs(b-d)) <= 3:
        print(1)
        return
    print(2)
do()