#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using pll = pair<ll, ll>;
#define drep(i, cc, n) for (ll i = (cc); i <= (n); ++i)
#define rep(i, n) drep(i, 0, n - 1)
#define all(a) (a).begin(), (a).end()
#define pb push_back
#define fi first
#define se second
mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
const ll MOD1000000007 = 1000000007;
const ll MOD998244353 = 998244353;
const ll MOD[3] = {999727999, 1070777777, 1000000007};
const ll LINF = 1LL << 60LL;
const int IINF = (1 << 30) - 1;


void solve(){
    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];

    priority_queue<tuple<int, int, int>, vector<tuple<int, int, int>>, greater<>> pq0, pq1;
    int di[4] = {0, 0, 1, -1}, dj[4] = {1, -1, 0, 0};
    vector<vector<int>> c(h, vector<int>(w, -1));
    c[0][0] = 1;
    c[h-1][w-1] = 0;
    pq1.push({a[0][1], 0, 1});
    pq1.push({a[1][0], 1, 0});
    pq0.push({a[h-2][w-1], h-2, w-1});
    pq0.push({a[h-1][w-2], h-1, w-2});

    vector<vector<bool>> visited0(h, vector<bool>(w, false));
    vector<vector<bool>> visited1(h, vector<bool>(w, false));
    visited0[h-1][w-1] = visited0[h-2][w-1] = visited0[h-1][w-2] = true;
    visited1[0][0] = visited1[1][0] = visited1[0][1] = true;

    int ans = 0;
    for(int turn=1; ; turn++){
        ans++;

        if(turn%2==0){
            auto [v, i, j] = pq0.top();
            pq0.pop();

            c[i][j] = 0;
            // check
            for(int k=0; k<4; k++){
                int nxt_i = i + di[k];
                int nxt_j = j + dj[k];

                if(nxt_i<0||nxt_j<0||h<=nxt_i||w<=nxt_j) continue;
                if(c[nxt_i][nxt_j] == 1){
                    cout << ans << '\n';
                    return;
                }
                if(c[nxt_i][nxt_j]==-1 && !visited0[nxt_i][nxt_j]){
                    pq0.push({a[nxt_i][nxt_j], nxt_i, nxt_j});
                    visited0[nxt_i][nxt_j] = true;
                }
            }
        }

        if(turn%2==1){
            auto [v, i, j] = pq1.top();
            pq1.pop();

            c[i][j] = 1;
            // check
            for(int k=0; k<4; k++){
                int nxt_i = i + di[k];
                int nxt_j = j + dj[k];

                if(nxt_i<0||nxt_j<0||h<=nxt_i||w<=nxt_j) continue;
                if(c[nxt_i][nxt_j] == 0){
                    cout << ans << '\n';
                    return;
                }
                if(c[nxt_i][nxt_j]==-1 && !visited1[nxt_i][nxt_j]){
                    pq1.push({a[nxt_i][nxt_j], nxt_i, nxt_j});
                    visited1[nxt_i][nxt_j] = true;
                }
            }
        }
    }
}

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int T=1;
    //cin >> T;
    while(T--) solve();
}