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

B=list(range(H*W))
B.sort(key=lambda x:A[x//W][x%W])
D=[[1]*W for _ in range(H)]

dd=[(0,1),(1,0),(-1,0),(0,-1)]

for p in B:
    i,j=divmod(p,W)
    for di,dj in dd:
        ni=i+di
        nj=j+dj
        if 0<=ni<H and 0<=nj<W:
            if A[ni][nj]>A[i][j]:
                D[ni][nj]=max(D[ni][nj],D[i][j]+1)

print(max(max(D[i]) for i in range(H)))