#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=n-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[9]={1,0,-1,0,1,1,-1,-1,0};
const ll dx[9]={0,-1,0,1,1,-1,1,-1,0};
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;
}

int main(){
    ll n,m;cin >> n >>m;vl v(n);
    rep(i,n){
        rep(j,m){
            ll a;cin >> a;v[i]+=a;
        }
    }
    ll dp[n+1][2];
    rep(i,n+1)rep(j,2)dp[i][j]=-INF;
    dp[0][0]=0;
    rep(i,n){
        chmax(dp[i+1][1],dp[i][0]+v[i]);
        chmax(dp[i+1][1],dp[i][1]);
        chmax(dp[i+1][0],dp[i][1]-v[i]);
        chmax(dp[i+1][0],dp[i][0]);
    }
    /*rep(i,n+1){
        cout << dp[i][0] <<" " << dp[i][1] <<endl;
    }*/
    cout << max(dp[n][0],dp[n][1]) <<endl;
}