#include<bits/stdc++.h>
#include<iostream>
using namespace std;
using LL = long long;
using P = pair<int,int>;
using Graph = vector<vector<int>>;
const int INF = 1 << 29;
const long long LINF = 1LL << 60;
#define all(x) (x).begin(), (x).end()
#define rep(i,n) for(int i = 0; i < (n); ++i)
template<class T>void chmin(T&a, T b){if(a > b) a = b;}
template<class T>void chmax(T&a, T b){if(a < b) a = b;}


int main(){
	int N, M; cin >> N >> M;
	vector<long long> A(N, 0);
	for(int i = 0; i < N; ++i){
		for(int j = 0; j < M; ++j){
			int tmp; cin >> tmp; A[i] += tmp;
		}
	}

	vector<vector<long long>> dp(N+1, vector<long long>(2, 0));
	
	for(int i = 0; i < N; ++i){
		//you choose the i-th sweets
		//now even
		if(i!=0)chmax(dp[i+1][1], dp[i][0] - A[i]);
		//now odd
		chmax(dp[i+1][0], dp[i][1] + A[i]);

		//you dont choose the i-th sweets
		chmax(dp[i+1][0], dp[i][0]);
		chmax(dp[i+1][1], dp[i][1]);
	}

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