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

pairs = []
for i in range(H):
    for j in range(W):
        pairs.append((A[i][j],i,j))
pairs.sort(reverse=True)

dp = [[-1]*W for _ in range(H)]
dij = [(-1,0),(1,0),(0,-1),(0,1)]
for a,i,j in pairs:
    maximum = 0
    for di,dj in dij:
        if 0 <= i+di <= H-1 and 0 <= j+dj <= W-1 and a < A[i+di][j+dj]:
            maximum = max(maximum,dp[i+di][j+dj])
    dp[i][j] = maximum+1

print(max([max(li) for li in dp]))