import sys
#sys.setrecursionlimit((1<<19)-1)
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
input=sys.stdin.buffer.readline

H,W=map(int,input().split())
A=[list(map(int,input().split())) for i in range(H)]
p=[]
for i in range(H):
    for j in range(W):
        p.append((A[i][j],i,j))
p.sort()
dp=[[1]*(W) for i in range(H)]
for a,i,j in p:
    for dx,dy in [(0,1),(1,0),(0,-1),(-1,0)]:
        try:
            assert i+dx>=0
            assert j+dy>=0
            if a>A[i+dx][j+dy]:
                dp[i][j]=max(dp[i][j],dp[i+dx][j+dy]+1)
        except:
            pass
ans=0
for i in dp:
    ans=max(ans,max(i))
print(ans)