import heapq

bit10 = (1 << 10) - 1

def solve(h, w, a):
  col = [[-1] * w for _ in range(h)]

  ans = 0
  num = (a[0][0] << 20) | 0
  queue0 = [num]
  num = (a[h-1][w-1] << 20) | (h-1 << 10) | w-1
  queue1 = [num]
  while True:
    ans += 1
    filled = False
    while True:
      if queue0:
        num = heapq.heappop(queue0)
        i = (num >> 10) & bit10
        j = num & bit10
        if col[i][j] != -1:
          continue
        filled = True
        col[i][j] = 0
        for di, dj in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
          ni, nj = i + di, j + dj
          if ni < 0 or ni >= h or nj < 0 or nj >= w:
            continue
          if col[ni][nj] == 0:
            continue
          elif col[ni][nj] == 1:
            return ans - 2
          else:
            num = (a[ni][nj] << 20) | (ni << 10) | nj
            heapq.heappush(queue0, num)
        if filled:
          break

    ans += 1
    while True:
      if queue1:
        num = heapq.heappop(queue1)
        i = (num >> 10) & bit10
        j = num & bit10
        if col[i][j] != -1:
          continue
        filled = True
        col[i][j] = 1
        for di, dj in [(1, 0), (-1, 0), (0, 1), (0, -1)]:
          ni, nj = i + di, j + dj
          if ni < 0 or ni >= h or nj < 0 or nj >= w:
            continue
          if col[ni][nj] == 1:
            continue
          elif col[ni][nj] == 0:
            return ans - 2
          else:
            num = (a[ni][nj] << 20) | (ni << 10) | nj
            heapq.heappush(queue1, num)
        if filled:
          break

def main():
  h, w = [int(x) for x in input().split()]
  a = [[int(x) for x in input().split()] for _ in range(h)]
  print(solve(h, w, a))

if __name__ == "__main__":
  main()