H, W = map(int, input().split())
A = [[0 for i in range(W)]] +  [list(map(int, input().split())) for i in range(H-2)] + [[0 for i in range(W)]]
d = [-1, 0, 1]
ans = 10**10
for i in range(1, H-1):
    now = i
    cunt = 0
    now_2 = i
    ok = True
    if A[now][0] != -1:
        cunt += A[now][0]
    else:
        continue
    for j in range(1, W):
        wall_now = 10**10
        for k in d:
            if now + k <= 0 or now + k >= H-1:
                continue   
            if A[now+k][j] == -1:
                continue   
            if wall_now > A[now+k][j]:
                wall_now = A[now+k][j]
                now_2 = i+k
        if wall_now == 10**10:
            ok = False
            break
        now = now_2    
        cunt += wall_now
    if ok:
        ans = min(ans, cunt)

if ans == 10**10:
	print(-1)
else:
	print(ans)