h,w = map(int,input().split())
a = [list(map(int,input().split())) for i in range(h)]
dp = [[0]*w for i in range(h)]
seen = [[0]*w for i in range(h)]

def dfs(i, j):
	if seen[i][j]:
		return dp[i][j]
	
	ret = 1
	for x, y in [(i+1, j), (i-1, j), (i, j+1), (i, j-1)]:
		if 0 <= x < h and 0 <= y < w and a[x][y] > a[i][j]:
			ret = max(ret, dfs(x, y) + 1)
	dp[i][j] = ret
	return ret

ans = 0
for i in range(h):
	for j in range(w):
		ans = max(ans, dfs(i, j))

print(ans)