from operator import itemgetter

H,W=map(int,input().split())

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

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

LIST.sort(key=itemgetter(0),reverse=True)

DP=[[1]*W for i in range(H)]

for w,i,j in LIST:
    for x,y in [(i+1,j),(i-1,j),(i,j+1),(i,j-1)]:
        if 0<=x<H and 0<=y<W:
            if A[x][y]>A[i][j]:
                DP[i][j]=max(DP[i][j],DP[x][y]+1)

ANS=0
for i in range(H):
    for j in range(W):
        ANS=max(ANS,DP[i][j])

print(ANS)