import heapq

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

  ans = 0
  queue0 = [(a[0][0], 0, 0)]
  queue1 = [(a[h-1][w-1], h-1, w-1)]
  while True:
    ans += 1
    filled = False
    while True:
      if queue0:
        _, i, j = heapq.heappop(queue0)
        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:
            heapq.heappush(queue0, (a[ni][nj], ni, nj))
        if filled:
          break

    ans += 1
    while True:
      if queue1:
        _, i, j = heapq.heappop(queue1)
        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:
            heapq.heappush(queue1, (a[ni][nj], ni, nj))
        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()