#include<iostream>
#include<string>
#include<iomanip>
#include<cmath>
#include<vector>
#include<algorithm>
#include<utility>

using namespace std;

#define int long long
#define endl "\n"

constexpr long long INF = (long long)1e18;
constexpr long long MOD = 1'000'000'007; 

struct fast_io {
	fast_io(){
		std::cin.tie(nullptr);
		std::ios::sync_with_stdio(false);
	};
} fio;

signed main(){
	cout<<fixed<<setprecision(10);
	
	int N, M;
    vector<int> A;
    vector<vector<int>> dp;
    cin>>N>>M;
    
    A.resize(N);
    dp.resize(N+1, vector<int>(2, -INF));
	
    for(int i = 0; i < N; i++){
        for(int j = 0; j < M; j++){
            int a;
            
            cin>>a;
            
            A[i] += a;
        }
    }
    
    dp[0][0] = 0;
    
    for(int i = 0; i < N; i++){
        dp[i+1][1] = max(dp[i][0] + A[i], max(dp[i+1][1], dp[i][1]));
        dp[i+1][0] = max(dp[i][1] - A[i], max(dp[i+1][0], dp[i][0]));
    }
    
    cout<<max(dp[N][0], dp[N][1])<<endl;
    
	return 0;
}