// Template
#include <bits/stdc++.h>
#define rep_override(x, y, z, name, ...) name
#define rep2(i, n) for (int i = 0; i < (int)(n); ++i)
#define rep3(i, l, r) for (int i = (int)(l); i < (int)(r); ++i)
#define rep(...) rep_override(__VA_ARGS__, rep3, rep2)(__VA_ARGS__)
#define per(i, n) for (int i = (int)(n) - 1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
using namespace std;
using ll = long long;
constexpr int inf = 1001001001;
constexpr ll INF = 3003003003003003003;
template <typename T> inline bool chmin(T& x, const T& y) {if (x > y) {x = y; return 1;} return 0;}
template <typename T> inline bool chmax(T& x, const T& y) {if (x < y) {x = y; return 1;} return 0;}
struct IOSET {IOSET() {cin.tie(0); ios::sync_with_stdio(0); cout << fixed << setprecision(10);}} ioset;

// Main
int main() {
    int n, m;
    cin >> n >> m;
    vector<vector<ll>> a(n, vector<ll>(m, 0));
    rep(i, n) rep(j, m) cin >> a[i][j];
    
    vector<ll> b(n, 0);
    rep(i, n) rep(j, m) b[i] += a[i][j];
    
    vector<vector<ll>> dp(n + 1, vector<ll>(2, -INF));
    dp[0][0] = 0;
    rep(i, n) rep(j, 2) {
        if (dp[i][j] == -INF) continue;
        chmax(dp[i + 1][j], dp[i][j]);
        if (j & 1) {
            chmax(dp[i + 1][0], dp[i][j] - b[i]);
        } else {
            chmax(dp[i + 1][1], dp[i][j] + b[i]);
        }
    }
    
    cout << max(dp[n][0], dp[n][1]) << "\n";
    return 0;
}