// Enjoy your stay. Code by evima #include using namespace std; using ld = long double; using ll = long long; using vl = vector; 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 v(n); rep(i, n) cin >> v[i]; return v; } template bool chmin(T& a, const T& b) { return (b < a) ? (a = b, true) : false; } template bool chmax(T& a, const T& b) { return (a < b) ? (a = b, true) : false; } template map freq(const vector& v){ map ret; for(T x: v) ++ret[x]; return ret; } template vector sorted(vector v) { sort(all(v)); return v; } template vector sub(const vector& v, int from, int to) { vector ret; copy(&v[from], &v[to], back_inserter(ret)); return ret; } template string str(const T& x, int prec = 20) { stringstream ss; ss << setprecision(prec) << x; return ss.str(); } template string str(const vector& v, int prec = 20) { stringstream ss; ss << setprecision(prec); rep(i, sz(v)) ss << v[i] << (i < sz(v) - 1 ? " " : ""); return ss.str(); } template void print1(T&& x, const string& end) { cout << str(x) << end; } void print() { print1("", "\n"); } template void print(T&& head, U&&... tail) { print1(head, " "); print(forward(tail)...); } template void eprint1(T&& x, const string& end) { cout << str(x) << end; } void eprint() { eprint1("", "\n"); } template void eprint(T&& head, U&&... tail) { eprint1(head, " "); eprint(forward(tail)...); } template void quit(T&&... x) { print(forward(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 zipmap(vl v) { map 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(); } }