import sys
input = sys.stdin.readline

from heapq import heappop,heappush

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

DP=[[1<<63]*W for i in range(H-2)]

Q=[]

for i in range(H-2):
    if A[i][0]!=-1:
        DP[i][0]=A[i][0]
        Q.append((DP[i][0],i,0))

Q.sort()

while Q:
    now,x,y=heappop(Q)

    if DP[x][y]!=now:
        continue

    for z in range(x-1,x+2):
        for w in range(y-1,y+2):
            if x==z and y==w:
                continue

            if 0<=z<H-2 and 0<=w<W:
                if A[z][w]==-1:
                    continue

                if now+A[z][w]<DP[z][w]:
                    DP[z][w]=now+A[z][w]
                    heappush(Q,(DP[z][w],z,w))

ANS=1<<63

for i in range(H-2):
    ANS=min(ANS,DP[i][-1])

if ANS==1<<63:
    print(-1)
else:
    print(ANS)