#include "bits/stdc++.h"
using namespace std;
#define int long long
#define REP(i, n) for (int i = 0; i < (int)n; ++i)
#define RREP(i, n) for (int i = (int)n - 1; i >= 0; --i)
#define FOR(i, s, n) for (int i = s; i < (int)n; ++i)
#define RFOR(i, s, n) for (int i = (int)n - 1; i >= s; --i)
#define ALL(a) a.begin(), a.end()
#define IN(a, x, b) (a <= x && x < b)
template<class T>istream&operator >>(istream&is,vector<T>&vec){for(T&x:vec)is>>x;return is;}
template<class T>inline void out(T t){cout << t << "\n";}
template<class T,class... Ts>inline void out(T t,Ts... ts){cout << t << " ";out(ts...);}
template<class T>inline bool CHMIN(T&a,T b){if(a > b){a = b;return true;}return false;}
template<class T>inline bool CHMAX(T&a,T b){if(a < b){a = b;return true;}return false;}
constexpr int INF = 1e18;



signed main(){
	int N, M;
	cin >> N >> M;
	vector<vector<int>>a(N, vector<int>(M));
	cin >> a;
	vector<int>b(N);
	REP(i, N) {
		REP(j, M) {
			b[i] += a[i][j];
		}
	}

	vector<vector<int>>dp(N + 1, vector<int>(2, -INF));
	dp[0][0] = 0;
	REP(i, N) {
		REP(k, 2) {
			CHMAX(dp[i + 1][k ^ 1], dp[i][k] + b[i] * (k ? -1 : 1));
			CHMAX(dp[i + 1][k], dp[i][k]);
		}
	}
	out(*max_element(ALL(dp[N])));
}