/* -*- coding: utf-8 -*-
 *
 * 2328.cc:  No.2328 Build Walls - yukicoder
 */

#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_H = 800;
const int MAX_W = 800;
const int MAX_N = MAX_H * MAX_W + 2;
const int INF = 1 << 30;

const int dxs[] = { 1, 1, 0, -1, -1, -1, 0, 1 };
const int dys[] = { 0, -1, -1, -1, 0, 1, 1, 1 };

/* typedef */

typedef pair<int,int> pii;
typedef vector<pii> vpii;

/* global variables */

int as[MAX_H][MAX_W], ds[MAX_N];
vpii nbrs[MAX_N];

/* subroutines */

/* main */

int main() {
  int h, w;
  scanf("%d%d", &h, &w);
  h -= 2;

  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) scanf("%d", as[i] + j);

  int st = h * w, gl = st + 1, n = gl + 1;

  for (int y = 0, u = 0; y < h; y++)
    for (int x = 0; x < w; x++, u++)
      if (as[y][x] >= 0)
	for (int di = 0; di < 8; di++) {
	  int vy = y + dys[di], vx = x + dxs[di], v = vy * w + vx;
	  if (vy >= 0 && vy < h && vx >= 0 && vx < w && as[vy][vx] >= 0)
	    nbrs[u].push_back(pii(v, as[vy][vx]));
	}

  for (int y = 0; y < h; y++) {
    if (as[y][0] >= 0) nbrs[st].push_back(pii(y * w, as[y][0]));
    if (as[y][w - 1] >= 0) nbrs[y * w + (w - 1)].push_back(pii(gl, 0));
  }

  fill(ds, ds + n, INF);
  ds[st] = 0;
  priority_queue<pii> q;
  q.push(pii(0, st));

  while (! q.empty()) {
    auto ue = q.top(); q.pop();
    int ud = -ue.first, u = ue.second;
    if (ds[u] != ud) continue;
    if (u == gl) break;

    for (auto &vw: nbrs[u]) {
      int v = vw.first, vd = ud + vw.second;
      if (ds[v] > vd) {
	ds[v] = vd;
	q.push(pii(-vd, v));
      }
    }
  }
  
  printf("%d\n", (ds[gl] < INF) ? ds[gl] : -1);
  return 0;
}