H,W = list(map(int,input().split()))
A = [list(map(int,input().split())) for i in range(H)]
B = []

for i in range(H):
    for j in range(W):
        B.append((A[i][j],i,j))

B.sort(key=lambda x:x[0])

from collections import defaultdict

DP = [[0]*W for i in range(H)]
ans = 0
for a, i, j in B:
    dp = 0
    if i > 0 and A[i-1][j] < a:
        dp = max(DP[i-1][j], dp)
    if j > 0 and A[i][j-1] < a:
        dp = max(DP[i][j-1], dp)
    if i < H-1 and A[i+1][j] < a:
        dp = max(DP[i+1][j], dp)
    if j < W-1 and A[i][j+1] < a:
        dp = max(DP[i][j+1], dp)
    DP[i][j] = dp + 1
    ans = max(dp+1,ans)
print(ans)