from collections import deque

h, w = map(int, input().split())
h -= 2
a = [list(map(int, input().split())) + [-1] for _ in range(h)] + [[-1] * (w + 1)]
INF = 10**18
dp = [[INF] * (w + 1) for _ in range(h)] + [[INF] * (w + 1)]
que = deque()
for i in range(h):
    if a[i][0] == -1:
        continue
    dp[i][0] = a[i][0]
    que.append((i, 0))

while que:
    x, y = que.popleft()
    for i in range(-1, 2):
        for j in range(-1, 2):
            sx = x + i
            sy = y + j
            if a[sx][sy] != -1 and dp[sx][sy] > dp[x][y] + a[sx][sy]:
                dp[sx][sy] = dp[x][y] + a[sx][sy]
                que.append((sx, sy))


ans = min(v[-2] for v in dp)
print(ans if ans < INF else -1)
# print(*dp, sep="\n")