#pragma GCC optimize("O3")
#include <bits/stdc++.h>
#define ll long long
#define rep(i,n) for(ll i=0;i<(n);i++)
#define pll pair<ll,ll>
#define pii pair<int,int>
#define pq priority_queue
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define endl '\n'
#define ios ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define lb(c,x) distance(c.begin(),lower_bound(all(c),x))
#define ub(c,x) distance(c.begin(),upper_bound(all(c),x))

using namespace std;

inline int topbit(unsigned long long x){
	return x?63-__builtin_clzll(x):-1;
}

inline int popcount(unsigned long long x){
	return __builtin_popcountll(x);
}

inline int parity(unsigned long long x){//popcount%2
	return __builtin_parity(x);
}



template<class T> inline bool chmax(T& a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T> inline bool chmin(T& a,T b){if(a>b){a=b;return 1;}return 0;}

const ll INF=1e15;

int main(){
    ll n,m;
    cin >> n >> m;
    
    vector<vector<ll>> dp(n+1,vector<ll>(n+1));
    vector<ll> a(n);
    ll ans=0;
    rep(i,n){
        ll sum=0;
        rep(j,m){
            ll x;
            cin >> x;
            sum+=x;
        }
        a[i]=sum;
    }
    dp[0][0]=0;
    for(ll i=1;i<=n;i++){
        for(ll j=1;j<=i;j++){
            dp[i][j]=max(dp[i][j],dp[i-1][j]);
            if(j%2==1){
                dp[i][j]=max(dp[i][j],dp[i-1][j-1]+a[i-1]);
            }
            else{
                dp[i][j]=max(dp[i][j],dp[i-1][j-1]-a[i-1]);
            }
        }
    }
    for(ll i=0;i<=n;i++){
        ans=max(dp[n][i],ans);
    }
    cout << ans << endl;
    return 0;
}