import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
input = sys.stdin.readline

#alist = list(map(int,input().split()))
#alist = []
#s = input()
h,w = map(int,input().split())
#for i in range(n):
#    alist.append(list(map(int,input().split())))
grid = [list(map(int,input().split())) for i in range(h)]
dp = [[1 for i in range(w)] for j in range(h)]
hq = []
for i in range(h):
    for j in range(w):
        heapq.heappush(hq,(grid[i][j],i,j))
dxy = [[-1,0],[1,0],[0,-1],[0,1]]
while hq:
    x,i,j = heapq.heappop(hq)
    for dx,dy in dxy:
        if 0 <= i+dx < h and 0 <= j+dy < w and grid[i+dx][j+dy] > x:
            dp[i+dx][j+dy] = max(dp[i+dx][j+dy],dp[i][j]+1)
ans = 0
for i in dp:
    ans = max(ans,max(i))
print(ans)