H,W=map(int,input().split())
A=[list(map(int,input().split())) for h in range(H)]
dp=[[1]*W for h in range(H)]
AHW=[(A[h][w],h,w) for h in range(H) for w in range(W)]
AHW.sort()
for a,h,w in AHW:
    for hh,ww in ((h-1,w),(h+1,w),(h,w-1),(h,w+1)):
        if 0<=hh<H and 0<=ww<W and A[hh][ww]<A[h][w]:
            dp[h][w]=max(dp[h][w],dp[hh][ww]+1)
ans=max(dp[h][w] for h in range(H) for w in range(W))
print(ans)