A, B, C, D = map(int, input().split())
X = abs(A-C)
Y = abs(B-D)
if X==0 or Y==0:
    print(1)
    exit()
if X<=1 and Y<=2:
    print(1)
    exit()
if X<=2 and Y<=1:
    print(1)
    exit()
print(2)