o BFS
from collections import deque
n, m = map(int, input().split())
graph = []
for i in range(n):
graph.append(list(map(int, input())))
dx = [0, 0, -1, 1] #상하좌우 순서임 x라서 좌우만
dy = [1, -1, 0, 0]
def BFS(x, y):
queue = deque()
queue.append((x, y))
while queue:
x, y = queue.popleft()
for i in range(4):
nx = x + dx[i]
ny = y + dy[i]
if (nx < 0 or ny < 0 or nx >= n or ny >= m):
continue
if (graph[nx][ny] == 0):
continue
if (graph[nx][ny] == 1):
graph[nx][ny] = graph[x][y] + 1
queue.append((nx, ny))
return graph[n - 1][m - 1]
print(BFS(0, 0)) #답 10
ex) 5 6
101010
111111
000011
111111
111111