#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <cmath>
using namespace std;
using ll = long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int n, m;
    cin >> n >> m;

    vector<ll> a(n);
    for (int i = 0; i < n; i++) {
        ll s = 0;
        for (int j = 0; j < m; j++) {
            ll t;
            cin >> t;
            s += t;
        }
        a[i] = s;
    }

    //dp[i] : a[i]まで使ってできる奇数個のブロックの最大価値
    vector<ll> dp(n);
    dp[0] = a[0];
    for (int i = 1; i < n; i++) {
        ll t = 1LL << 60, s = 0;
        for (int h = i - 1; h > 0; h--) {
            t = min(t, a[h]);
            s = max(s, dp[h - 1] - t);
        }
        dp[i] = max(s + a[i], dp[i - 1]);
    }
    
    cout << dp[n - 1] << endl;

    return 0;
}