from heapq import heappush, heappop
inf = float('inf')


def dijkstra(s, g, N):
    # ゴールがない場合はg=-1とする。

    def cost(v, m):
        return v * N + m

    dist = [inf] * N
    mindist = [inf] * N
    seen = [False] * N
    Q = [cost(0, s)]
    while Q:
        c, m = divmod(heappop(Q), N)
        if seen[m]:
            continue
        seen[m] = True
        dist[m] = c
        if m == g:
            return dist

        #------heapをアップデートする。--------
        for u, C in G[m]:
            if seen[u]:
                continue
            newdist = dist[m] + C

            #------------------------------------
            if newdist >= mindist[u]:
                continue
            mindist[u] = newdist
            heappush(Q, cost(newdist, u))
    return dist

H, W = map(int, input().split())
A = [[-1] * (W + 1)]
for i in range(H - 2):
    A.append(list(map(int, input().split())) + [-1])
A.append([-1] * (W + 1))

N = (H + 1) * (W + 1)
def f(h, w):
    return h * (W + 1) + w
    
G = [[] for i in range(N)]
for i in range(H):
    if A[i][0] == -1:
        continue
    G[0].append((f(i, 0), A[i][0]))

ddx = [1, 1, 1, 0, 0, -1, -1, -1]
ddy = [1, 0, -1, 1, -1, 1, 0, -1]
for h in range(H):
    for w in range(W + 1):
        if A[h][w] == -1:
            continue
        for dx, dy in zip(ddx, ddy):
            x = h + dx
            y = w + dy
            if A[x][y] == -1:
                continue
            G[f(h, w)].append((f(x, y), A[x][y]))

D = dijkstra(0, -1, N)
ans = inf
for i in range(H):
    ans = min(ans, D[f(i, W - 1)])

print(ans) if ans != inf else print(-1)