a,b=map(int,input().split())
c,d=map(int,input().split())
if (a==c and b==d):
    print(0)
elif ((a+b)==(c+d)) or ((a-b)==(c-d)) or abs(a-c)+abs(b-d)<=3:
    print(1)
elif (abs(a-c)+abs(b-d))<=6 or (abs((a+b)-(c+d))<=3) or (abs((a-b)-(c-d))<=3) or (a+b)%2==(c+d)%2:
    print(2)
else:
    print(3)