h,w=map(int,input().split())
a=[list(map(int,input().split()))for i in range(h)]
t=[]
for i in range(h):
	for j in range(w):
		t.append((a[i][j], i, j))
t.sort()
t=t[::-1]

dp=[[0]*w for i in range(h)]
for val, i, j in t:
	dp[i][j] = 1
	for v in [(i-1, j),(i+1, j),(i, j-1),(i, j+1)]:
		if 0 <= v[0] < h and 0 <= v[1] < w and a[v[0]][v[1]] > val:
			dp[i][j] = max(dp[i][j], dp[v[0]][v[1]] + 1)

ans = 0
for i in range(h):
	for j in range(w):
		ans = max(ans, dp[i][j])

print(ans)