import sys

sys.setrecursionlimit(10**5)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def MI(): return map(int, sys.stdin.buffer.readline().split())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
inf = 10**16
md = 10**9+7
# md = 998244353

a,b,c,d=MI()
if a==c and b==d:
    ans=0
elif abs(a-c)+abs(b-d)<=3:
    ans=1
else:
    ans=2
print(ans)