import sys
from itertools import permutations
from heapq import heappop,heappush
from collections import deque
import random
import bisect

input = lambda :sys.stdin.readline().rstrip()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

H,W = mi()
A = [li() for i in range(H)]

INF = 10**9
dp = [[-INF]*W for i in range(H)]

idx = [(i,j) for i in range(H) for j in range(W)]
idx.sort(key=lambda x:A[x[0]][x[1]])

for (i,j) in idx[::-1]:
    dp[i][j] = 1
    for dx,dy in [(-1,0),(0,1),(1,0),(0,-1)]:
        ni,nj = i+dx,j+dy
        if 0 <= ni < H and 0 <= nj < W and dp[ni][nj]!=-INF and A[ni][nj] > A[i][j]:
            dp[i][j] = max(dp[i][j],dp[ni][nj]+1)

res = max(max(dp[i]) for i in range(H))
print(res)