from sys import setrecursionlimit, stdin
from collections import defaultdict, deque, Counter
from itertools import permutations, combinations, product
from functools import lru_cache
from bisect import bisect_left, bisect_right
from heapq import heappush, heappop
from copy import copy, deepcopy
from decimal import Decimal
from random import random, randrange

# from pypyjit import set_param
# set_param('max_unroll_recursion=-1')

setrecursionlimit(1 << 20)
readline = stdin.readline
INF = 10 ** 18
MOD = 998244353
# MOD = 1000000007
ALP = 26
''' Input '''
def I(): return int(readline())
def ST(): return readline()[:-1]
def LI(): return list(map(int, readline().split()))
def LII(): return list(map(lambda x: int(x) - 1, readline().split()))
def LF(x, func): return [func() for _ in [0] * x]
def SPI(): return map(int, readline().split())
def SPII(): return map(lambda x: int(x) - 1, readline().split())
def FIE(x): return [readline()[:-1] for _ in [0] * x]

''' Array '''
def cmin(dp, i, x):
    if x < dp[i]: dp[i] = x
def cmax(dp, i, x):
    if x > dp[i]: dp[i] = x

''' Alphabet '''
def alp_a_to_i(s): return ord(s) - ord('a')
def alp_A_to_i(s): return ord(s) - ord('A')
def alp_i_to_a(i): return chr(ord('a') + i)
def alp_i_to_A(i): return chr(ord('A') + i)

''' Other'''
def nynx(y, x, H, W): return [(y + dy, x + dx) for dy, dx in [(-1, 0), (1, 0), (0, -1), (0, 1)] if 0 <= y + dy < H and 0 <= x + dx < W]
def gen(x, *args):
    if len(args) == 1: return [x] * args[0]
    if len(args) == 2: return [[x] * args[1] for _ in [0] * args[0]]
    if len(args) == 3: return [[[x] * args[2] for _ in [0] * args[1]] for _ in [0] * args[0]]
    if len(args) == 4: return [[[[x] * args[3] for _ in [0] * args[2]] for _ in [0] * args[1]] for _ in [0] * args[0]]

''' Output '''
def pprint(E): 
    print()
    for e in E: print(e)
def Yes(): print("Yes")
def No(): print("No")
def YES(): print("YES")
def NO(): print("NO")
def yn(x): print("Yes" if x else "No")
def YN(x): print("YES" if x else "NO")
###############################################################################################


class Dikstra:
    def __init__(self, N, node):
        self.node = node 
        self.N = N 

    def get(self, start):
        self.start_node = start
        dist, done = [10 ** 18] * self.N, [0] * self.N
        hq = [(0, start)] # (cost, node)
        dist[start] = 0
        while hq:
            c, v = heappop(hq)
            if done[v]: continue
            done[v] = 1
            for to, cost in self.node[v]: 
                new_cost = dist[v] + cost
                if not done[to] and new_cost < dist[to]:
                    dist[to] = new_cost
                    heappush(hq, (dist[to], to))
        return dist


H, W = SPI()
A = LF(H - 2, LI)
A = [[-1] * W] + A + [[-1] * W]

def f(i, j):
    return i * W + j

def inside(y, x): return 0 <= y < H and 0 <= x < W

node = [[] for _ in range(H * W)]
for i in range(1, H - 1):
    for j in range(W):
        if A[i][j] == -1: continue

        if inside(i + 1, j) and A[i + 1][j] != -1:
            node[f(i, j)].append((f(i + 1, j), A[i + 1][j]))
        
        if inside(i - 1, j) and A[i - 1][j] != -1:
            node[f(i, j)].append((f(i - 1, j), A[i - 1][j]))

        if inside(i, j + 1) and A[i][j + 1] != -1:
            node[f(i, j)].append((f(i, j + 1), A[i][j + 1]))
    
        if inside(i + 1, j + 1) and A[i + 1][j + 1] != -1:
            node[f(i, j)].append((f(i + 1, j + 1), A[i + 1][j + 1]))

        if inside(i - 1, j + 1) and A[i - 1][j + 1] != -1:
            node[f(i, j)].append((f(i - 1, j + 1), A[i - 1][j + 1]))


dist = [INF] * (H * W)
done = [0] * (H * W)
hq = []
for i in range(1, H - 1):
    if A[i][0] != -1:
        heappush(hq, (A[i][0], f(i, 0)))
        dist[f(i, 0)] = A[i][0]

while hq:
    c, v = heappop(hq)
    if done[v]: continue
    done[v] = 1
    for to, cost in node[v]: 
        new_cost = dist[v] + cost
        if not done[to] and new_cost < dist[to]:
            dist[to] = new_cost
            heappush(hq, (dist[to], to))

ans = INF
for i in range(1, H - 1):
    ans = min(ans, dist[f(i, W - 1)])

if ans == INF: ans = -1
print(ans)