from collections import deque
H,W=map(int,input().split())
A=[list(map(int,input().split())) for _ in range(H)]
G=[[] for _ in range(H*W)]
into_num=[0]*(H*W)
def xy_to_x_y(xy):
    return xy//W,xy%W
def x_y_to_xy(x,y):
    return x*W+y
dx=[0,1,0,-1]
dy=[1,0,-1,0]
for i in range(H):
    for j in range(W):
        for k in range(4):
            new_x=i+dx[k]
            new_y=j+dy[k]
            if(0<=new_x<H and 0<=new_y<W and A[i][j]<A[new_x][new_y]):
                ij=x_y_to_xy(i,j)
                new_xy=x_y_to_xy(new_x,new_y)
                G[ij].append(new_xy)
                into_num[new_xy]+=1
que=deque()
dp=[0]*(H*W)
for i in range(H*W):
    if(into_num[i]==0):
        que.append(i)
while len(que):
    p=que.popleft()
    for q in G[p]:
        dp[q]=max(dp[q],dp[p]+1)
        into_num[q]-=1
        if(into_num[q]==0):
            que.append(q)
print(max(dp)+1)