#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
#define D pair<int,P>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }

const int dx[] = { 1,0,-1,0,1,1,-1,-1 };
const int dy[] = { 0,-1,0,1,1,-1,1,-1 };
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int h, w; cin >> h >> w;
	h -= 2;
	vector a(h, vector<int>(w));
	rep(i, h)rep(j, w)cin >> a[i][j];
	priority_queue<D, vector<D>, greater<D>> q;
	vector dp(h, vector<int>(w, INF));
	rep(i, h) {
		if (-1 == a[i][0])continue;
		q.push({ a[i][0],{ i,0 } });
		dp[i][0] = a[i][0];
	}
	while (!q.empty()) {
		auto tmp = q.top();
		q.pop();
		long long cost = tmp.first;
		int x = tmp.second.first;
		int y = tmp.second.second;
		if (cost > dp[x][y]) continue;
		rep(i, 8) {
			int nx = x + dx[i];
			int ny = y + dy[i];
			if ((0 <= nx) && (h > nx) && (0 <= ny) && (w > ny) && (-1 != a[nx][ny])) {
				if (chmin(dp[nx][ny], dp[x][y] + a[nx][ny])) q.push({ dp[nx][ny], { nx,ny } });
			}
		}
	}
	int ans = INF;
	rep(i, h)chmin(ans, dp[i][w - 1]);
	if (INF == ans)ans = -1;
	cout << ans << endl;
	return 0;
}