import io
import sys

_INPUT = """\
6
5 4
2 5 7 11
1 6 9 10
3 4 8 12
5 4
2 5 -1 11
-1 6 9 10
3 -1 8 12
5 4
2 5 -1 11
-1 -1 -1 10
3 -1 8 12
"""

def solve(test):
  inf=10**20
  H,W=map(int,input().split())
  A=[list(map(int,input().split())) for _ in range(H-2)]
  dp=[inf]*((H-2)*W)
  def idx(i,j): return i*W+j
  for i in range(H-2):
    if A[i][0]!=-1: dp[idx(i,0)]=A[i][0]
  for j in range(W-1):
    for i in range(H-2):
      if A[i][j+1]!=-1:
        for k,l in [(i-1,j),(i,j),(i+1,j)]:
          if 0<=k<H-2:
            dp[idx(i,j+1)]=min(dp[idx(i,j+1)],dp[idx(k,l)]+A[i][j+1])
  ans=min([dp[idx(i,W-1)] for i in range(H-2)])
  if ans==inf: ans=-1
  if test==0:
    print(ans)
  else:
    return None

def random_input():
  from random import randint,shuffle
  N=randint(1,10)
  M=randint(1,N)
  A=list(range(1,M+1))+[randint(1,M) for _ in range(N-M)]
  shuffle(A)
  return (" ".join(map(str, [N,M]))+"\n"+" ".join(map(str, A))+"\n")*3

def simple_solve():
  return []

def main(test):
  if test==0:
    solve(0)
  elif test==1:
    sys.stdin = io.StringIO(_INPUT)
    case_no=int(input())
    for _ in range(case_no):
      solve(0)
  else:
    for i in range(1000):
      sys.stdin = io.StringIO(random_input())
      x=solve(1)
      y=simple_solve()
      if x!=y:
        print(i,x,y)
        print(*[line for line in sys.stdin],sep='')
        break

#0:提出用、1:与えられたテスト用、2:ストレステスト用
main(0)