#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
constexpr int INF = 1e9;
constexpr long long LINF = 1e17;
constexpr int MOD = 1000000007;
constexpr double PI = 3.14159265358979323846;

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