#include <bits/stdc++.h>
using namespace std;
#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
// using mint = modint1000000007;
// using mint = double;
#endif

//define
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<long long , long long>;
using vi = vector<int>;
using vll = vector<long long>;

#define rep(i,l,r) for (int i = (int)(l); i < (int)(r); i++)
#define rrep(i,l,r) for (int i = (int)(r-1); i >= (int)(l); i--)
#define len(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define elif else if
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
const int inf = 1e9;
const long long infl = 1LL<<60;
const int mod = 998244353;
ll pow(ll a, ll b, ll p){ ll ans = 1; while(b){ if(b & 1) (ans *= a) %= p; (a *= a) %= p; b /= 2; } return ans; }
template<class T, class U> bool chmin(T& a, const U& b){ if(a > T(b)){ a = b; return 1; } return 0; }
template<class T, class U> bool chmax(T& a, const U& b){ if(a < T(b)){ a = b; return 1; } return 0; }
template <class T>
using spq = priority_queue<T, vector<T>, greater<T>>;

template<class T>istream& operator>>(istream& i, vector<T>& v) {for(int j = 0; j < (int)(v).size(); j++) i >> v[j]; return i;}
struct IoSetup {
    IoSetup() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(15);
        cerr << fixed << setprecision(15);
    }
} iosetup;

void solve(){
    int n, m; cin >> n >> m;
    vector a(n, vll(m, 0));
    rep(i, 0, n) cin >> a[i];
    
    mcf_graph<int, ll> g(2 + n + n * m + m);
    int s = (m + 1) * n;
    int t = s + 1;
    int off = t + 1;
    int h = n / 2;
    rep(i, 0, h){
        int d = (m + 1) * i;
        g.add_edge(s, d, 1, 0);
        rep(j, 0, m){
            int p = i * (m + 1) + j + 1;
            g.add_edge(d, p, 1, a[i][j]);
            g.add_edge(p, off + j, 1, 0);
        }
    }
    rep(i, n-h, n){
        int d = (m + 1) * i;
        g.add_edge(d, t, 1, 0);
        rep(j, 0, m){
            int p = i * (m + 1) + j + 1;
            g.add_edge(p, d, 1, inf - a[i][j]);
            g.add_edge(off + j, p, 1, 0);
        }
    }
    // cout << off + m -1 << " " << 2 + n + n * m + m << endl;
    auto [f, r] =  g.flow(s, t);
    cout << (ll)inf * h - r << endl;
    return ;
}


int main(){
    int t;
    // cin >> t;
    t = 1;
    while(t--) solve();
    return 0;
}