H,W=map(int,input().split())
L=[list(map(int,input().split())) for _ in range(H)]
q=[]
for h in range(H):
  for w in range(W):
    q.append((L[h][w],h,w))
dp=[[1]*W for _ in range(H)]
q.sort()
dhw=[(1,0),(-1,0),(0,1),(0,-1)]
ans=1
for x,h,w in q:
  for dh,dw in dhw:
    if 0<=h+dh<H and 0<=w+dw<W and L[h][w]<L[h+dh][w+dw]:
      dp[h+dh][w+dw]=max(dp[h+dh][w+dw],dp[h][w]+1)
      if ans<dp[h+dh][w+dw]:
        ans=dp[h+dh][w+dw]
print(ans)