#include <bits/stdc++.h>
using namespace std;

vector<int> di = {-1, 0, 1, 0};
vector<int> dj = {0, 1, 0, -1};

int main() {
    int h, w;
    cin >> h >> w;
    vector<vector<int>> a(h, vector<int>(w));
    for (int i = 0; i < h; i++) {
        for (int j = 0; j < w; j++) {
            cin >> a[i][j];
        }
    }
    auto inc = [&](int i, int j) {
        return (0 <= i && i < h && 0 <= j && j < w);
    };
    vector<vector<int>> b(h, vector<int>(w, -1));
    vector<vector<vector<bool>>> visit(2, vector<vector<bool>>(h, vector<bool>(w, false)));
    b[0][0] = 1;
    visit[1][0][0] = true;
    b[h - 1][w - 1] = 0;
    visit[0][h - 1][w - 1] = true;
    vector<priority_queue<tuple<int, int, int>, vector<tuple<int, int, int>>, greater<tuple<int, int, int>>>> pq(2);
    pq[1].push({a[0][1], 0, 1});
    visit[1][0][1] = true;
    pq[1].push({a[1][0], 1, 0});
    visit[1][1][0] = true;
    pq[0].push({a[h - 1][w - 2], h - 1, w - 2});
    visit[0][h - 1][w - 2] = true;
    pq[0].push({a[h - 2][w - 1], h - 2, w - 1});
    visit[0][h - 2][w - 1] = true;
    int cnt = 0;
    while (true) {
        cnt++;
        int id = cnt % 2;
        auto [x, i, j] = pq[id].top();
        pq[id].pop();
        b[i][j] = id;
        bool ok = true;
        for (int k = 0; k < 4; k++) {
            int ni = i + di[k], nj = j + dj[k];
            if (!inc(ni, nj)) {
                continue;
            }
            if (b[ni][nj] == 1 - id) {
                ok = false;
            } else if (b[ni][nj] == -1 && !visit[id][ni][nj]) {
                visit[id][ni][nj] = true;
                pq[id].push({a[ni][nj], ni, nj});
            }
        }
        if (!ok) {
            break;
        }
    }
    cout << cnt << endl;
}