#include <bits/stdc++.h>
using namespace std;
template <class F> class y_combinator {
    F f;

   public:
    y_combinator(F&& f) : f(std::forward<F>(f)) {}
    template <class... Args> auto operator()(Args&&... args) const { return f(*this, std::forward<Args>(args)...); }
};
using ll = long long;
using ld = long double;
template <class T, class U = std::less<T>> using prique = std::priority_queue<T, std::vector<T>, U>;
template <class T> T floor(T a, T b) noexcept { return a / b - (a % b && (a ^ b) < 0); }
template <class T> T ceil(T a, T b) noexcept { return floor(a + b - 1, b); }
template <class T> bool chmin(T& x, const T& y) noexcept { return (x > y ? x = y, true : false); }
template <class T> bool chmax(T& x, const T& y) noexcept { return (x < y ? x = y, true : false); }
#define overload4(a, b, c, d, e, ...) e
#define rep1(a) for (long long _i = 0; _i < (a); _i++)
#define rep2(i, a) for (long long i = 0; i < (a); i++)
#define rep3(i, a, b) for (long long i = (a); i < (b); i++)
#define rep4(i, a, b, c) for (long long i = (a); i < (b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)
#define rrep(i, a, b, c) for (long long i = (a); i > (b); i += (c))
#define all(x) std::begin(x), std::end(x)
#define rall(x) std::rbegin(x), std::rend(x)
#define pb push_back
#ifndef LOCAL
#define debug(...)
#endif

int main() {
    int N, M;
    cin >> N >> M;
    vector<ll> S(N);
    rep(i, N) {
        rep(j, M) {
            ll a;
            cin >> a;
            S[i] += a;
        }
    }
    const ll inf = -1e18;
    vector<vector<ll>> dp(N + 1, vector<ll>(2, inf));
    dp[0][0] = 0;
    rep(i, N) {
        if(dp[i][1] != inf)chmax(dp[i + 1][0], dp[i][1] - S[i]);
        if(dp[i][0] != inf)chmax(dp[i + 1][1], dp[i][0] + S[i]);
        chmax(dp[i + 1][0], dp[i][0]);
        chmax(dp[i + 1][1], dp[i][1]);
    }
    cout << max(dp[N][0], dp[N][1]) << "\n";
}