#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (int)(n); i ++)
#define irep(i,n) for (int i = (int)(n) - 1;i >= 0;--i)
using namespace std;
using ll = long long;
using PL = pair<ll,ll>;
using P = pair<int,int>;
constexpr int INF = 1000000000;
constexpr long long HINF = 1000000000000000;
constexpr long long MOD = 1000000007;// = 998244353;
constexpr double EPS = 1e-4;
constexpr double PI = 3.14159265358979;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int N,M; cin >> N >> M;
    vector<ll> A(N);
    rep(i,N) {
        ll x = 0;
        rep(j,M) {
            ll a; cin >> a;
            x += a;
        }
        A[i] = x;
    }

    vector<vector<ll>> dp(N + 1,vector<ll>(N + 1,0));
    rep(i,N) {
        rep(j,N) {
            dp[i + 1][j + 1] = max(dp[i][j + 1],dp[i][j] + (j%2 ? -1: 1) * A[i]);
        }
    }
    ll ans = 0;
    rep(i,N + 1) {
        ans = max(ans,dp[N][i]);
    }
    cout << ans << '\n'; 
    return 0;
}