H,W=map(int,input().split())
H-=2
A=[list(map(int,input().split())) for i in range(H)]
INF=10**10
for i in range(H):
    for j in range(W):
        if A[i][j]==-1:
            A[i][j]=INF
from heapq import *
D=[[INF]*W for i in range(H)]
Q=[]
heapify(Q)
for i in range(H):
    heappush(Q,(A[i][0],i,0))
    D[i][0]=A[i][0]
while len(Q):
    v=heappop(Q)
    x,y=v[1],v[2]
    if v[0]>D[x][y]:
        continue
    for i in range(-1,2):
        for j in range(-1,2):
            p,q=x+i,y+j
            if 0<=p and 0<=q and p<H and q<W:
                if D[x][y]+A[p][q]<D[p][q]:
                    D[p][q]=D[x][y]+A[p][q]
                    heappush(Q,(D[p][q],p,q))
ANS=min([D[i][-1] for i in range(H)])
if ANS<INF:
    print(ANS)
else:
    print(-1)