#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
    ll N, M;
    cin >> N >> M;
    vector<vector<ll>> A(N);
    vector<ll> sum(N);
    for (int i = 0; i < N; i++) {
        A[i].resize(M);
        for (int j = 0; j < M; j++) {
            cin >> A[i][j];
            sum[i] += A[i][j];
        }
    }

    ll dp[N + 1][2] = {};
    for (int i = 0; i < N; i++) {
        dp[i + 1][1] = max(dp[i][1], dp[i][0] + sum[i]);
        dp[i + 1][0] = max(dp[i][0], dp[i][1] - sum[i]);

        // cerr << "i=" << i << "dp[i+1][0] = " << dp[i + 1][0] << "dp[i+1][1] = " << dp[i + 1][1] << endl;
    }

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

    return 0;
}