from collections import deque

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

dx=[0,1,0,-1]
dy=[1,0,-1,0]
def dfs(vx,vy,walk):
    global ans
    ans = max(ans, walk)
    for x,y in zip(dx,dy):
        vvx = vx+x
        vvy = vy+y
        if not (0<=vvx<H) or not (0<=vvy<W):
            continue
        if (vvx,vvy) in seen:
            continue
        if A[vvx][vvy]>A[vx][vy]:
            dfs(vvx,vvy,walk+1)
        else:
            continue

global ans
ans = 0
for i in range(H):
    for j in range(W):
        seen = set()
        dfs(i,j,1)
print(ans)