#include <fstream>

using namespace std;

ifstream cin("flip.in");
ofstream cout("flip.out");

int a[17][17],i,n,m,j,slin[17],scol[17], s, slin2, scol2;
void citire()
{
 cin >> n >> m;
 for (i = 1 ; i <= n; i ++)
    for (j = 1; j <= m; j++)
        {cin >> a[i][j];
         slin[i] = slin[i] + a[i][j];
         scol[j] = scol[j] + a[i][j];
        }
}


void afisare()
{
 for (i = 1; i <= n; i ++)
    for (j = 1; j <= m; j++)
        s = s + a[i][j];
 cout<<s;
}

int main()
{
 citire();
 for (i = 1 ; i <= n; i++)
    {
     for (j = 1; j <= m; j++)
        {
              slin2 = 0;
              scol2 = 0;
              for (int k = 1; k <= m; k ++)
                 slin2 = slin2 + a[i][k];
              if (slin2 < 0)
                {
                 for (int o = 1 ; o <= m; o ++)
                    a[i][o] = a[i][o] * -1;
                }
             for (int k = 1; k <= n; k ++)
                 scol2 = scol2 + a[k][j];
                         if (scol2 < 0)
                {
                 for (int o = 1; o <= n; o ++)
                    a[o][j] = a[o][j] * -1;
                }
              slin2 = 0;
              scol2 = 0;
             for (int k = 1; k <= m; k ++)
                 slin2 = slin2 + a[i][k];
        }
    }

afisare();
}