#include <bits/stdc++.h>
//#include <chrono>
//#pragma GCC optimize("Ofast")
using namespace std;
#define reps(i,s,n) for(int i = s; i < n; i++)
#define rep(i,n) reps(i,0,n)
#define Rreps(i,n,e) for(int i = n - 1; i >= e; --i)
#define Rrep(i,n) Rreps(i,n,0)
#define ALL(a) a.begin(), a.end()
#define fi first
#define se second
typedef long long ll;
typedef vector<ll> vec;
typedef vector<vec> mat;

ll N,M,H,W,Q,K,A,B;
string S;
typedef pair<ll, ll> P;
const ll INF = (1LL<<58);

template<class T> bool chmin(T &a, const T &b){
    if(a > b) {a = b; return true;}
    else return false;
}
template<class T> bool chmax(T &a, const T &b){
    if(a < b) {a = b; return true;}
    else return false;
}

int main() {
    cin>>N>>M;
    vec score(N);
    rep(i,N){
        vec temp(M);
        rep(j, M) cin>>temp[j];
        score[i] = accumulate(ALL(temp), 0LL);
    }
    vec dp(2, 0);
    dp[1] = -INF;
    rep(i,N){
        ll temp = max(dp[1], dp[0] + score[i]);
        chmax(dp[0], dp[1] - score[i]);
        chmax(dp[1], temp);
    }
    cout<<max(dp[0], dp[1])<<endl;
}