#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int INF = 1e9 + 10;
const ll INFL = 4e18;

const vector<int> dx = {0, 1, 0, -1};
const vector<int> dy = {1, 0, -1, 0};

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];
        }
    }

    vector<priority_queue<tuple<int, int, int>, vector<tuple<int, int, int>>, greater<tuple<int, int, int>>>> pq(2);
    pq[0].push({A[0][0], 0, 0});
    pq[1].push({A[H - 1][W - 1], H - 1, W - 1});

    vector<vector<vector<bool>>> vst(2, vector<vector<bool>>(H, vector<bool>(W, false)));

    int ans = 0;
    bool fin = false;

    int i = 0;
    while (true) {
        auto [a, x, y] = pq[i % 2].top();
        pq[i % 2].pop();

        if (vst[i % 2][x][y]) {
            continue;
        }

        vst[i % 2][x][y] = true;

        for (int j = 0; j < 4; j++) {
            int nx = x + dx[j];
            int ny = y + dy[j];

            if (nx < 0 || nx >= H || ny < 0 || ny >= W) {
                continue;
            }
            if (vst[i % 2][nx][ny]) {
                continue;
            }

            if (vst[(i + 1) % 2][nx][ny]) {
                ans = i - 1;
                fin = true;
                break;
            }

            pq[i % 2].push({A[nx][ny], nx, ny});
        }

        if (fin) {
            break;
        }

        i++;
    }

    cout << ans << endl;
}