#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>
#include <map>
#include <queue>
#include <iomanip>
#include <set>
#include <tuple>
#define mkp make_pair
#define mkt make_tuple
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define all(v) v.begin(),v.end()
using namespace std;
typedef long long ll;
const ll MOD=1e9+7;
template<class T> void chmin(T &a,const T &b){if(a>b) a=b;}
template<class T> void chmax(T &a,const T &b){if(a<b) a=b;}

const ll INF=1e18;

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int N,M;
  cin>>N>>M;
  vector<vector<ll>> A(N,vector<ll>(M));
  rep(i,N) rep(j,M) cin>>A[i][j];

  vector<ll> sum(N,0);
  rep(i,N) rep(j,M) sum[i]+=A[i][j];

  vector<vector<ll>> dp(N+1,vector<ll> (2,-INF));
  dp[0][0]=0;
  for(int i=0;i<N;i++) for(int j=0;j<2;j++){
    if(dp[i][j]==-INF) continue;
    chmax(dp[i+1][j],dp[i][j]);
    if(j==0) chmax(dp[i+1][1-j],dp[i][j]+sum[i]);
    else chmax(dp[i+1][1-j],dp[i][j]-sum[i]);
  }
  ll ans=*max_element(all(dp[N]));
  cout<<ans<<endl;

  return 0;
}