H,W=map(int,input().split())
A=[list(map(int,input().split())) for i in range(H)]
L=[]
for i in range(H):
  for j in range(W):
    L.append((A[i][j],i,j))
L.sort()
dp=[[1]*W for i in range(H)]
DX=[1,0,-1,0]
DY=[0,1,0,-1]
for i in range(len(L)):
  x,y=L[i][1],L[i][2]
  for dx,dy in zip(DX,DY):
    x2,y2=x+dx,y+dy
    if x2<0 or x2>=H or y2<0 or y2>=W:
      continue
    if A[x][y]<=A[x2][y2]:
      continue
    dp[x][y]=max(dp[x][y],dp[x2][y2]+1)
result=0
for i in range(H):
  result=max(result,max(dp[i]))
print(result)