#include <bits/stdc++.h>
using std::cin;
using std::cout;
using std::endl;
using ll = long long;
std::mt19937 rnd(std::chrono::steady_clock::now().time_since_epoch().count());

template <class T> inline bool chmax(T &a, T b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}

template <class T> inline bool chmin(T &a, T b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}

const int inf = (int)1e9 + 7;
const long long INF = 1LL << 62;

template <int mod> struct ModInt {
    int x;

    ModInt() : x(0) {}

    ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    ModInt &operator+=(const ModInt &p) {
        if ((x += p.x) >= mod)
            x -= mod;
        return *this;
    }

    ModInt &operator-=(const ModInt &p) {
        if ((x += mod - p.x) >= mod)
            x -= mod;
        return *this;
    }

    ModInt &operator*=(const ModInt &p) {
        x = (int)(1LL * x * p.x % mod);
        return *this;
    }

    ModInt &operator/=(const ModInt &p) {
        *this *= p.inverse();
        return *this;
    }

    ModInt operator-() const { return ModInt(-x); }

    ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

    ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

    ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

    ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

    bool operator==(const ModInt &p) const { return x == p.x; }

    bool operator!=(const ModInt &p) const { return x != p.x; }

    ModInt inverse() const {
        int a = x, b = mod, u = 1, v = 0, t;
        while (b > 0) {
            t = a / b;
            std::swap(a -= t * b, b);
            std::swap(u -= t * v, v);
        }
        return ModInt(u);
    }

    ModInt pow(int64_t n) const {
        ModInt ret(1), mul(x);
        while (n > 0) {
            if (n & 1)
                ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }

    friend std::ostream &operator<<(std::ostream &os, const ModInt &p) { return os << p.x; }

    friend std::istream &operator>>(std::istream &is, ModInt &a) {
        int64_t t;
        is >> t;
        a = ModInt<mod>(t);
        return (is);
    }

    static int get_mod() { return mod; }
};

constexpr int mod = (int)1e9 + 7;
using mint = ModInt<mod>;

void solve() {
    int H, W;
    cin >> H >> W;
    std::vector a(H, std::vector<ll>(W)), d(H, std::vector<ll>(W, INF));
    for (int i = 1; i < H - 1; i++) {
        for (int j = 0; j < W; j++) {
            cin >> a[i][j];
        }
    }

    using T = std::tuple<ll, int, int>;
    std::priority_queue<T, std::vector<T>, std::greater<>> pq;
    for (int i = 1; i < H - 1; i++) {
        if (a[i][0] == -1)
            continue;
        d[i][0] = a[i][0];
        pq.emplace(d[i][0], i, 0);
    }
    const int dr[] = {0, 1, 0, -1, 1, 1, -1, -1};
    const int dc[] = {1, 0, -1, 0, 1, -1, 1, -1};
    while (not pq.empty()) {
        auto [dist, r, c] = pq.top();
        pq.pop();
        if (dist > d[r][c])
            continue;
        for (int i = 0; i < 8; i++) {
            const int nr = r + dr[i];
            const int nc = c + dc[i];
            if (nr <= 0 or nr >= H - 1 or nc < 0 or nc > W - 1 or a[nr][nc] == -1)
                continue;
            if (chmin(d[nr][nc], d[r][c] + a[nr][nc])) {
                pq.emplace(d[nr][nc], nr, nc);
            }
        }
    }
    ll res = INF;
    for (int i = 1; i < H - 1; i++) {
        chmin(res, d[i][W - 1]);
    }
    if (res == INF)
        res = -1;
    cout << res << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    int I_love_KKT89 = 1;
    // cin >> I_love_KKT89;
    for (int Case = 1; Case <= I_love_KKT89; ++Case) {
        // cout << "Case #" << Case << ": ";
        solve();
    }
    return 0;
}