from heapq import heappop, heappush

h, w = map(int, input().split())
A = []
A.append([-1 for _ in range(w)])
for _ in range(h - 2):
    A.append(list(map(int, input().split())))
A.append([-1 for _ in range(w)])

H = []
INF = 10**18
DP = [[INF for _ in range(w)] for _ in range(h)]
for i in range(h):
    if A[i][0] != -1:
        DP[i][0] = A[i][0]
        heappush(H, (DP[i][0], i, 0))
Directions = [(1, 0), (1, 1), (0, 1), (-1, 1), (-1, 0), (-1, -1), (0, -1), (1, -1)]
while H:
    cc, ci, cj = heappop(H)
    if cc > DP[ci][cj]:
        continue
    for di, dj in Directions:
        ni, nj = ci + di, cj + dj
        if 0 <= ni < h and 0 <= nj < w:
            if A[ni][nj] == -1:
                continue
            nc = cc + A[ni][nj]
            if nc >= DP[ni][nj]:
                continue
            DP[ni][nj] = nc
            heappush(H, (nc, ni, nj))
ans = INF
for i in range(h):
    ans = min(ans, DP[i][-1])
if ans == INF:
    ans = -1
print(ans)