#include <bits/stdc++.h>
#include <atcoder/all>
#define int long long
#define endl "\n"
#define all(n) n.begin(),n.end()
#define rall(n) n.rbegin(),n.rend()
#define rep(i, s, n) for (int i = s; i < (int)(n); i++)
#define floatset(n) fixed<<setprecision(n)
#define rangeout(x,y,h,w) (x<0||y<0||h-1<x||w-1<y)
using namespace std;
using namespace atcoder;
template<class T>using vec=vector<T>;
template<class T>using min_queue=priority_queue<T,vector<T>,greater<T>>;
using ll = long long;
using ld = long double;
using pll = pair<ll,ll>;
using Graph = vector<vector<int>>;
struct Edge1{ll to,cost;};
using WGraph = vec<vec<Edge1>>;
struct BellEdge{ll from,to,cost;};
using BGraph=vec<BellEdge>;
constexpr ll INF = 1e18;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr int dx[4]={1,0,-1,0};
constexpr int dy[4]={0,1,0,-1};
template<typename T>
bool chmin(T&a,T b){return a>b?a=b,true:false;}
template<typename T>
bool chmax(T&a,T b){return a<b?a=b,true:false;}
bool Flag(int bit,int i){return (bit&(1LL<<i));}
template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    fill( (T*)array, (T*)(array+N), val );
}
int dp[1010][2];
signed main(){
    int N,M;
    cin>>N>>M;
    vec<int>A(N);
    for(int i=0;i<N;i++){
        for(int j=0;j<M;j++){
            int a;
            cin>>a;
            A[i]+=a;
        }
    }
    for(int i=0;i<N;i++){
        dp[i+1][1]=max(dp[i][0]+A[i],dp[i][1]);
        dp[i+1][0]=max(dp[i][1]-A[i],dp[i][0]);
    }
    cout<<max(dp[N][0],dp[N][1])<<endl;
}