#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
constexpr int Inf = 2000000010;
constexpr ll INF= 2000000000000000000;
constexpr ll MOD = 1000000007;
const double PI = 3.1415926535897;
typedef pair<int,int> P;
typedef pair<int,P> PP;

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;
}

ll mod(ll val, ll M) {
    ll res = val % M;
    if(res < 0) {
        res += M;
    }
    return res;
}

template<typename T>
T RS(T N, T P, T M){
    if(P == 0) {
        return 1;
    }
    if(P < 0) {
        return 0;
    }
    if(P % 2 == 0){
        ll t = RS(N, P/2, M);
        if(M == -1) return t * t;
        return t * t % M;
    }
    if(M == -1) {
        return N * RS(N,P - 1,M);
    }
    return N * RS(N, P-1, M) % M;
}

ll dp[1010][2] = {-INF}; //dp[i][j] = i番目のお菓子まででの幸せ度の最大値、ただしj = 0の時は正、j = 1の時は負

int main() {
    int N,M;
    cin >> N >> M;
    vector<ll> vec(N);
    for(int i = 0;i < N;i++) {
        ll cnt = 0;
        for(int j = 0;j < M;j++) {
            ll A;
            cin >> A;
            cnt += A;
        }
        vec.at(i) = cnt;
    }
    dp[0][0] = 0;
    for(int i = 0;i < N;i++) {
        chmax(dp[i + 1][0],dp[i][1] - vec.at(i));
        chmax(dp[i + 1][0],dp[i][0]);
        chmax(dp[i + 1][1],dp[i][0] + vec.at(i));
        chmax(dp[i + 1][1],dp[i][1]);
    }
    cout << max(dp[N][0],dp[N][1]) << endl;
}