# include <stdio.h>
int r,c,i,h,suma_finala=0;
int tabel[100][100];
bool com = true;
int citire()
{
    for(i=1;i<=r;i++)
    {
         for(h=1;h<=c;h++)
         {
             scanf("%d", &tabel[i][h]);
         }
    }
}
int comutare_randuri()
{
    int suma;
    for(i=1;i<=r;i++)
    {
        suma = 0;
        for(h=1;h<=c;h++)
             suma += tabel[i][h];               
        if(suma < 0){
             for(h=1;h<=c;h++)
                  tabel[i][h] = tabel[i][h] * -1;
                  com = true;
        }
                  
    }   
}
int comutare_coloane()
{
    int suma_temp;
    for(h=1;h<=c;h++)
    {
        suma_temp = 0;
        for(i=1;i<=r;i++)
             suma_temp = suma_temp + tabel[i][h];
        if(suma_temp < 0){
              suma_temp = suma_temp * -1;
                  com = true;      
              }
        suma_finala = suma_finala + suma_temp;
    }
}
int main()
{
    freopen("flip.in","r",stdin);
    freopen("flip.out","w",stdout);
    scanf("%d %d", &r, &c);
    citire();
    while(com == true)
    {
        com = false;
        comutare_randuri();
        comutare_coloane();
    }
    printf("%d\n", suma_finala);
    return 0;
}