#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")

#include<bits/stdc++.h>
using namespace std;
using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
ll MOD = 998244353;
ll MAX = 1e18;
vector<ll> dx = {0,0,1,1,1,-1,-1,-1},dy = {1,-1,0,1,-1,0,1,-1};
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    ll H,W;
    cin >> H >> W;
    vector<vector<ll>> A(H,vector<ll>(W,-1));
    for(ll i = 1;i < H - 1;i++){
        for(ll j = 0;j < W;j++){
            cin >> A[i][j];
        }
    }
    vector<vector<ll>> memo(H,vector<ll>(W,-1));
    priority_queue<tuple<ll,ll,ll>,vector<tuple<ll,ll,ll>>,greater<tuple<ll,ll,ll>>> que;
    for(ll i = 0;i < H;i++){
        if(A[i][0] != -1){
            que.push(make_tuple(A[i][0],i,0));
        }
    }
    ll ans = MAX;
    while(!que.empty()){
        ll cost,x,y;
        tie(cost,x,y) = que.top();
        que.pop();
        if(memo[x][y] == -1){
            memo[x][y] = cost;
            if(y == W - 1){
                ans = min(ans,cost);
                continue;
            }
            for(ll i = 0;i < 8;i++){
                ll nx = x + dx[i],ny = y + dy[i];
                if(nx < 0 || nx >= H || ny < 0 || ny >= W) continue;
                if(A[nx][ny] == -1) continue;
                que.push(make_tuple(cost + A[nx][ny],nx,ny));
            }
        }   
    }
    if(ans == MAX) cout << -1 << endl;
    else cout << ans << endl;
}