import heapq
H,W=map(int,input().split())
A=[list(map(int,input().split())) for _ in range(H)]
v=[]
for i in range(H):
    for j in range(H):
        v.append((A[i],i,j))
v.sort()

INF=int(1e18)
dist=[[INF for _ in range(W)] for _ in range(H)]

for (_,i,j) in v:
    if dist[i][j]<INF:continue
    dist[i][j]=-1
    Q=[]
    heapq.heapify(Q)
    heapq.heappush(Q,(dist[i][j],(i,j)))
    
    while len(Q):
        d,(pi,pj)=heapq.heappop(Q)
        if dist[pi][pj]!=d:continue
        for (di,dj) in [(1,0),(-1,0),(0,1),(0,-1)]:
            ni=pi+di
            nj=pj+dj
            if ni not in range(H) or nj not in range(W):continue
            if A[pi][pj]>=A[ni][nj]:continue
            if dist[pi][pj]-1<dist[ni][nj]:
                dist[ni][nj]=dist[pi][pj]-1
                heapq.heappush(Q,(dist[ni][nj],(ni,nj)))
ans=INF
for i in range(H):
    for j in range(W):
        ans=min(ans,dist[i][j])
print(-ans)