H,W=map(int, input().split())
A=[];B=[];D={}

for i in range(H):
  AA=list(map(int, input().split()))
  A.append(AA)
  for j in range(W):
    a=AA[j]
    if a not in D:
      D[a]=[]
      B.append(a)
    D[a].append((i,j))
B=sorted(B)

dp=[[1]*W for _ in range(H)]
dy,dx=[1,-1,0,0],[0,0,1,-1]
for b in B:
  if b==1:
    continue 
  for y,x in D[b]:
    for i in range(4):
      ny,nx=y+dy[i],x+dx[i]
      if 0<=ny<H and 0<=nx<W and A[ny][nx]<A[y][x]:
        dp[y][x]=max(dp[y][x],dp[ny][nx]+1)
ans=0
for h in range(H):
  for w in range(W):
    ans=max(ans,dp[h][w])
print(ans)