import heapq
ds=[[0,1],[1,1],[-1,1],[1,0],[-1,0]]
def daiku():
    hq=[]
    for i in range(H-2):
        if A[i][0]!=-1:
            heapq.heappush(hq,[A[i][0],(i,0)])
    high=[[-1 for _ in range(W)] for _ in range(H)]
    while len(hq)!=0:
        h,p=heapq.heappop(hq)
        if high[p[0]][p[1]]==-1:
            high[p[0]][p[1]]=h
            for dx,dy in ds:
                x,y=p
                x+=dx
                y+=dy
                if 0<=x<H-2 and 0<=y<W and A[x][y]!=-1:
                    heapq.heappush(hq,[h+A[x][y],(x,y)])
    return high

H,W=map(int,input().split())
A=[]
for i in range(H-2):
    A.append(list(map(int,input().split())))
dist=daiku()
ans=10**12
for i in range(H-2):
    if dist[i][-1]!=-1:
        ans=min(ans,dist[i][-1])
if ans>=10**12:
    print(-1)
else:
    print(ans)