# 1412

line=input().split(" ")
pos=[int(line[i]) for i in range(len(line))]

distX=abs(pos[2]-pos[0])
distY=abs(pos[3]-pos[1])
if distX==0 and distY==0:
    times=0
elif distX==0 or distY==0:
    times=1
elif distX+distY<=3:
    times=1
else:
    times=2

print(times)