#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    int a[100][100],n,m,sn=0,sl=0,smax=0,i,j;
    ifstream f("flip.in");
    ofstream g("flip.out");
    f>>n>>m;
    for(i=0;i<n;i++)for(j=0;j<m;j++)f>>a[i][j];
    for(i=0;i<n;i++)for(j=0;j<n;j++){sn=sn+a[i][j];
                                      sl=sl+(a[i][j]*(-1));}
                                      if(sl>sn)for(j=0;j<n;j++)a[i][j]=a[i][j]*(-1);
    for(i=0;i<n;i++)for(j=0;j<n;j++)smax=smax+a[i][j];
    cout<<smax;
    f.close();
    g.close();
    return 0;
}