#include<bits/stdc++.h>
using namespace std;
const int INF = 1<<30;
const int MOD = 998244353;
//const long long INF = 1LL<<60;
using graph = vector<vector<int>>;
using ll = long long;

int dx[] = {1, 0, -1, 0};
int dy[] = {0, -1, 0, 1};

void print(vector<vector<int>> & vec, int h, int w){
    for (int i=0; i < h; i++){
        for (int j=0; j < w; j++){
            cout << vec[i][j];
        }
        cout << endl;
    }
}

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<vector<int>> region1(h, vector<int>(w)), region0(h, vector<int>(w));
    priority_queue<tuple<int, int, int>> pq1, pq0;
    pq1.push(make_tuple(-a[0][0], 0, 0));
    pq0.push(make_tuple(-a[h-1][w-1], h-1, w-1));
    
    for (int i=1; i <= h*w; i++){
        if (i % 2 == 1){
            int v, x, y;
            tie(v, x, y) = pq1.top();
            pq1.pop();
            if (region0[x][y] != 0){
                cout << i-2 << endl;
                return 0;
            }
            region1[x][y] = 2;
            for (int j=0; j < 4; j++){
                int nx = x + dx[j];
                int ny = y + dy[j];
                if (nx < 0 || h <= nx || ny < 0 || w <= ny) continue;
                if (region1[nx][ny] == 0){
                    region1[nx][ny] = 1;
                    pq1.push(make_tuple(-a[nx][ny], nx, ny));
                }
                continue;
            }
        }
        if (i % 2 == 0){
            int v, x, y;
            tie(v, x, y) = pq0.top();
            pq0.pop();
            region0[x][y] = 2;
            //cout << i << x << y << v << endl;
            if (region1[x][y] != 0){
                cout << i-2 << endl;
                return 0;
            }
            for (int j=0; j < 4; j++){
                int nx = x + dx[j];
                int ny = y + dy[j];
                if (nx < 0 || h <= nx || ny < 0 || w <= ny) continue;
                if (region0[nx][ny] == 0){
                    region0[nx][ny] = 1;
                    pq0.push(make_tuple(-a[nx][ny], nx, ny));
                }
            }
        }
    }
}