import std;

// ダイクストラ
// (H-2)*(W+1)の頂点をおいて、8方向に有向辺を張る

void read(T...)(string S, ref T args) {
    auto buf = S.split;
    foreach (i, ref arg; args) {
        arg = buf[i].to!(typeof(arg));
    }
}

void read_array(T)(string S, ref T[] arg) {
    arg = S.split.to!(T[]);
}

void main () {
    int H, W; readln.read(H, W);
    int[][] A = new int[][](H-2, W);
    foreach (i; 0..H-2) {
        readln.read_array(A[i]);
        A[i] = 0 ~ A[i];
    }

    solve(H, W, A);
}

struct pair {
    int x;
    int y;
}

bool isValid (int[][] A, int x, int y) {
    if (x < 0 || y < 0 || A.length <= y || A[0].length <= x) {
        return false;
    }
    if (A[y][x] == -1) {
        return false;
    }
    return true;
}

void connectPath (ref Dijkstra!pair G, int[][] A, int x, int y) {
    int[] dx = [-1, 0, 1];
    int[] dy = [-1, 0, 1];
    foreach (i; 0..dx.length) {
        foreach (j; 0..dy.length) {
            if (i == 1 && j == 1) {
                continue;
            }
            if (isValid(A, x+dx[i], y+dx[j])) {
                G.input(pair(x, y), pair(x+dx[i], y+dy[j]), A[y+dy[j]][x+dx[i]]);
            }
        }
    }
}

void solve (int H, int W, int[][] A) {
    auto G = Dijkstra!pair();
    foreach (X; 0..cast(int)A[0].length) {
        foreach (Y; 0..cast(int)A.length) {
            if (A[Y][X] == -1) {
                continue;
            }
            connectPath(G, A, X, Y);
        }
    }

    long ans = long.max;
    G.calculate(pair(0, 0));
    foreach (Y2; 0..H-2) {
        if (pair(W, Y2) in G.node) {
            ans = min(ans, G.cost(pair(W, Y2)));
            //G.trace(pair(W, Y2)).writeln;
            //writeln(G.cost(pair(W, Y2)));
        }
    }

    if (ans == long.max) {
        writeln(-1);
    } else {
        writeln(ans);
    }
}

struct Dijkstra(T) {
    T[][T] graph;
    long[T][T] weight;

    struct dijkstra_pair {
        long distance;
        T path;
        T vertex;
    }
    dijkstra_pair[T] node;
    private bool is_calculated = false;

    // 頂点の型Tであるグラフの辺と重みを受け取る
    void input (T u, T v, long w) {
        graph[u] ~= v;
        weight[u][v] = w;

        node[u] = dijkstra_pair(long.max, u, u);
        node[v] = dijkstra_pair(long.max, v, v);
    }

    // ダイクストラのアルゴリズムに基づいて頂点startからの(連結成分の)最小重みを求める
    void calculate (T start) {
        if (start !in node) {
            stderr.writeln("Fatal error in dijkstra.calculate(T start) : This vertex is not in the graph!");
            return;
        }

        // 以前の計算のリセット
        if (is_calculated) {
            foreach (ref x; node) {
                x.distance = long.max;
                x.path = x.vertex;
            }
        }

        node[start].distance = 0;
        node[start].path = start;

        // 優先度付きキューの宣言
        BinaryHeap!(Array!dijkstra_pair, "b.distance < a.distance") PQueue;
        PQueue.insert(node[start]);
        int count = 0;

        while (!PQueue.empty) {
            auto begin = PQueue.front; PQueue.removeFront;
            if (node[begin.vertex].distance < begin.distance) {
                continue;
            }

            if (begin.vertex in graph) {
                foreach (ref x; graph[begin.vertex]) {
                    if (node[begin.vertex].distance + weight[begin.vertex][x] < node[x].distance) {
                        node[x].distance = node[begin.vertex].distance + weight[begin.vertex][x];
                        node[x].path = begin.vertex;
                        PQueue.insert(node[x]);
                    }
                }
            }
        }

        is_calculated = true;
    }

    // 経路復元
    T[] trace (T end) {
        DList!T Q;
        T way = end;
        while (node[way].path != way) {
            Q.insertFront(way);
            way = node[way].path;
        }
        Q.insertFront(way);
        T[] ret;
        while (!Q.empty) {
            ret ~= Q.front; Q.removeFront;
        }
        return ret;
    }

    // 頂点endへの最小重みを出力 パスが存在しなければlong.maxを返す。
    long cost (T end) {
        if (end !in node) {
            stderr.writeln("Fatal error in dijkstra.cost(T end) : This vertex is not in the graph!");
            return long.max;
        }
        if (!is_calculated) {
            stderr.writeln("Costs are not calculatd. Do \"dijkstra.calculate(T start)\" first.");
            return long.max;
        }
        return node[end].distance;
    }
}