#include <bits/stdc++.h>
#define FOR(i, a, n) for(ll i = (ll)a; i < (ll)n; i++)
#define FORR(i, n) for(ll i = (ll)n - 1LL; i >= 0LL; i--)
#define rep(i, n) FOR(i, 0, n)
#define ALL(x) begin(x), end(x)
using namespace std;
using ll = long long;
constexpr ll Mod = 998244353;
constexpr ll mod = 1e9 + 7;
constexpr ll inf = 1LL << 60;
const double PI = acos(-1);
template <typename T1, typename T2> inline bool chmax(T1 &a, T2 b) {
    return a < b && (a = b, true);
}
template <typename T1, typename T2> inline bool chmin(T1 &a, T2 b) {
    return a > b && (a = b, true);
}
/*-------------------------------------------*/

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

    int n, m;
    cin >> n >> m;
    vector<ll> a(n);
    rep(i, n) {
        rep(j, m) {
            ll b;
            cin >> b;
            a[i] += b;
        }
    }

    vector<vector<ll>> dp(n + 1, vector<ll>(2, -inf));

    dp[0][0] = 0;
    rep(i, n) {
        chmax(dp[i + 1][0], dp[i][0]);
        chmax(dp[i + 1][1], dp[i][1]);
        chmax(dp[i + 1][1], dp[i][0] + a[i]);
        chmax(dp[i + 1][0], dp[i][1] - a[i]);
    }

    cout << max(dp[n][0], dp[n][1]) << endl;

    return 0;
}