# import pypyjit
# pypyjit.set_param("max_unroll_recursion=-1")
from collections import *
from functools import *
from itertools import *
from heapq import *
import sys, math,random,time
# input = sys.stdin.readline

H,W = map(int,input().split())
A = [tuple(map(int,input().split())) for _ in range(H)]

def nb(x,y):
    tmp = []
    if x+1<H:
        tmp.append((x+1,y))
    if x-1>=0:
        tmp.append((x-1,y))
    if y+1<W:
        tmp.append((x,y+1))
    if y-1>=0:
        tmp.append((x,y-1))
    return tmp
N = H*W
e = [[] for _ in range(N)]
ind = [0]*N
for i in range(H):
    for j in range(W):
        for ix,iy in nb(i,j):
            if A[i][j]<A[ix][iy]:
                e[W*i+j].append(W*ix+iy)
                ind[W*ix+iy] += 1

val = [-1]*N
v = deque()
for i in range(N):
    if ind[i]==0:
        val[i] = 1
        v.append(i)

while v:
    x = v.popleft()
    for ix in e[x]:

        val[ix] = max(val[ix],val[x]+1)
        ind[ix] -= 1
        if ind[ix]==0:
            v.append(ix)
print(max(val))