from collections import deque

N, M = map(int, input().split())
paper = []
cheese = 0
for i in range(N) :
    paper.append(list(map(int, input().split())))
    for n in paper[i] :
        if n == 1 :
            cheese += 1 
  
dx = [1,-1,0,0]
dy = [0,0,1,-1]          
q = deque()
time = 0

while cheese != 0 :
    visited = [[0]*M for _ in range(N)]
    q.append((0,0))
    visited[0][0] = 1
    
    while q :
        cx, cy = q.popleft()
        
        for i in range(4) :
            nx, ny = cx + dx[i], cy + dy[i]
            
            if 0<=nx<M and 0<=ny<N and paper[ny][nx] == 0 and visited[ny][nx] == 0 :
                q.append((nx, ny))
                visited[ny][nx] = 1
                
                for j in range(4) :
                    nnx, nny = nx+dx[j], ny+dy[j]
                    
                    if 0<=nnx<M and 0<=nny<N and paper[nny][nnx] == 1 :
                        visited[nny][nnx] += 1
    
    for i in range(N) :
        for j in range(M) :
            if paper[i][j] == 1 and visited[i][j] >= 2 :
                paper[i][j] = 0
                cheese -= 1
    
    time += 1

print(time)