from heapq import heappop, heappush


def dijkstra(s, n, edge):
  inf = float("inf")
  ans = [inf] * n
  ans[s] = 0
  root = [-1] * n
  h = [[0, s]]
  while h:
    c, v = heappop(h)
    if ans[v] < c:
      continue
    for u, t in edge[v]:
      if c + t < ans[u]:
        ans[u] = c + t
        root[u] = v
        heappush(h, [c + t, u])
  return [ans, root]


h, w = map(int, input().split())
a = [list(map(int, input().split())) for _ in range(h - 2)]
def ij(i, j): return i * w + j


edge = [[]for _ in range((h - 2) * w + 2)]
d = [
    [-1, -1],
    [-1, 0],
    [-1, 1],
    [0, -1],
    [0, 1],
    [1, -1],
    [1, 0],
    [1, 1]
]
inf = 10**10
for i in range(h - 2):
  for j in range(w):
    for di, dj in d:
      if 0 <= i + di < h - 2 and 0 <= j + dj < w:
        if a[i + di][j + dj] == -1:
          edge[ij(i, j)].append((ij(i + di, j + dj), inf))
        else:
          edge[ij(i, j)].append((ij(i + di, j + dj), a[i + di][j + dj]))
for i in range(h - 2):
  if a[i][0] == -1:
    edge[(h - 2) * w].append((ij(i, 0), inf))
  else:
    edge[(h - 2) * w].append((ij(i, 0), a[i][0]))
  edge[ij(i, w - 1)].append(((h - 2) * w + 1, 0))
ans = dijkstra((h - 2) * w, (h - 2) * w + 2, edge)[0]
if ans[(h - 2) * w + 1] >= inf: print(-1)
else: print(ans[(h - 2) * w + 1])