#include <bits/stdc++.h>

using namespace std;
void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}
int main() {
    fast_io();
    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];
        }
    }
    using tiii = tuple<int, int, int>;
    priority_queue<tiii, vector<tiii>, greater<tiii>> pq[2];
    pq[1].push({a[0][1], 0, 1});
    pq[1].push({a[1][0], 1, 0});
    pq[0].push({a[h - 2][w - 1], h - 2, w - 1});
    pq[0].push({a[h - 1][w - 2], h - 1, w - 2});
    vector<vector<int>> col(h, vector<int>(w));
    col[0][0] = -1;
    col[h - 1][w - 1] = 1;
    int dx[] = {0, 0, 1, -1};
    int dy[] = {1, -1, 0, 0};
    auto is_in = [&](int x, int y) {
        return 0 <= x && x < h && 0 <= y && y < w;
    };
    int ans = 0;
    while (true) {
        ans++;
        int i = -1, j = -1;
        while (!pq[ans % 2].empty()) {
            auto [aa, ii, jj] = pq[ans % 2].top();
            pq[ans % 2].pop();
            if (col[ii][jj] == 0) {
                i = ii;
                j = jj;
                break;
            }
        }
        assert(i != -1);
        assert(j != -1);
        col[i][j] = ans % 2 == 0 ? 1 : -1;
        for (int d = 0; d < 4; d++) {
            int ni = i + dx[d], nj = j + dy[d];
            if (!is_in(ni, nj)) {
                continue;
            }
            if (col[ni][nj] == 0) {
                pq[ans % 2].push({a[ni][nj], ni, nj});
            } else if (col[ni][nj] != col[i][j]) {
                cout << ans << endl;
                return 0;
            }
        }
    }
    cout << ans << endl;
}