def Map():
  return list(map(int,input().split()))

H,W = Map()
A = [Map() for i in range(H)]
G = [[] for i in range(H*W)]
dir = [(-1,0),(1,0),(0,1),(0,-1)]
D = [0 for i in range(H*W)]
for h in range(H):
  for w in range(W):
    u = h*W + w
    for dh,dw in dir:
      hh,ww = h + dh,w + dw
      if 0 <= hh < H and 0 <= ww < W:
        v = hh*W + ww
        if A[h][w] < A[hh][ww]:
          G[v].append(u)
          D[u] += 1

dp = [0 for i in range(H*W)]
S = []
for i in range(H*W):
  if D[i] == 0:
    S.append(i)
    dp[i] = 1

while len(S):
  v = S.pop()
  for u in G[v]:
    D[u] -= 1
    dp[u] = max(dp[u],dp[v] + 1)
    if D[u] == 0:
      S.append(u)
print(max(dp))