// Enjoy your stay. Code by evima

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

using ld = long double;
using ll = long long;
using vl = vector<ll>;
using LOOPVAR_TYPE = ll;

#define all(x) (x).begin(), (x).end()
#define sq(x) ((x) * (x))
#define sz(x) ll((x).size())
#define GET_MACRO(_1, _2, _3, NAME, ...) NAME
#define rep1(i, n) rep2(i, 0, n)
#define rep2(i, a, b) for(LOOPVAR_TYPE i = LOOPVAR_TYPE(a); i < LOOPVAR_TYPE(b); i++)
#define rep(...) GET_MACRO(__VA_ARGS__, rep2, rep1)(__VA_ARGS__)

#define eb emplace_back
#define fir first
#define sec second

const ld EPS = 1e-9;
const ld PI = 3.14159265358979323846L;
const ll INF = 1070000000LL;
const ll MOD = 998244353LL;// 1000000007LL;

void fast_io() { cin.tie(NULL); ios_base::sync_with_stdio(false); }
ll ll_input() { ll x; cin >> x; return x; }
string input() { string s; cin >> s; return s; }
vl vl_input(int n) { vector<ll> v(n); rep(i, n) cin >> v[i]; return v; }
template<class T> bool chmin(T& a, const T& b) { return (b < a) ? (a = b, true) : false; }
template<class T> bool chmax(T& a, const T& b) { return (a < b) ? (a = b, true) : false; }
template<class T> map<T, ll> freq(const vector<T>& v){ map<T, ll> ret; for(T x: v) ++ret[x]; return ret; }
template<class T> vector<T> sorted(vector<T> v) { sort(all(v)); return v; }
template<class T> vector<T> sub(const vector<T>& v, int from, int to) { vector<T> ret; copy(&v[from], &v[to], back_inserter(ret)); return ret; }
template<class T> string str(const T& x, int prec = 20) { stringstream ss; ss << setprecision(prec) << x; return ss.str(); }
template<class T> string str(const vector<T>& v, int prec = 20) { stringstream ss; ss << setprecision(prec); rep(i, sz(v)) ss << v[i] << (i < sz(v) - 1 ? " " : ""); return ss.str(); }
template<class T> void print1(T&& x, const string& end) { cout << str(x) << end; }
void print() { print1("", "\n"); }
template<class T, class... U> void print(T&& head, U&&... tail) { print1(head, " "); print(forward<U>(tail)...); }
template<class T> void eprint1(T&& x, const string& end) { cout << str(x) << end; }
void eprint() { eprint1("", "\n"); }
template<class T, class... U> void eprint(T&& head, U&&... tail) { eprint1(head, " "); eprint(forward<U>(tail)...); }
template<class... T> void quit(T&&... x) { print(forward<T>(x)...); exit(0); }
void yn(bool cnd, const string& yes = "Yes", const string& no = "No") { if(cnd) print(yes); else print(no); }
void zip(vl& v) { vl w = v; sort(all(w)); int n = unique(all(w)) - w.begin(); for(ll& x: v) x = lower_bound(&w[0], &w[n], x) - &w[0]; }
map<ll, ll> zipmap(vl v) { map<ll, ll> ret; sort(all(v)); v.erase(unique(all(v)), v.end()); rep(i, sz(v)) ret[v[i]] = i; return ret; }

ll a[1010], dp[1010][2];

void solveOne(){
    ll N, M;
    cin >> N >> M;
    rep(i, N){
        vl A = vl_input(M);
        a[i] = reduce(all(A));
    }
    rep(i, N + 1){
        rep(j, 2){
            dp[i][j] = i == 0 && j == 0 ? 0 : -2e18;
        }
    }
    rep(i, N){
        rep(j, 2){
            chmax(dp[i + 1][j], dp[i][j]);
            chmax(dp[i + 1][(j + 1) % 2], dp[i][j] + a[i] * (j ? -1 : 1));
        }
    }
    print(max(dp[N][0], dp[N][1]));
}

int main(){
    fast_io();
    
    int num_tc = 1;
    // cin >> num_tc;
    
    
    
    rep(tc, 1, num_tc + 1){
        // cout << "Case #" << tc << ": " ;// << endl;
        solveOne();
    }
}