#include <stdio.h>
//#include <stdlib.h>

int main()
{
    char t;
    FILE * fin=fopen("flip.in","r");
    FILE * fout=fopen("flip.out","w");
    int N,M,m[16][16];
    int i,j;
    int Sp,S=0;
    fscanf(fin,"%d%d",&M,&N);
    for (i=0;i<N;i++)
        for (j=0;j<M;j++)
        {
            fscanf(fin,"%d",&(m[i][j]));
        }
    for (i=0;i<N;i++)
    {
        Sp=0;
        for (j=0;j<M;j++)
        {
            Sp+=m[i][j];
        }
        if (Sp<0)
        {
            for (j=0;j<M;j++)
            {
                m[i][j]=-m[i][j];
            }
        }
    }
    for (j=0;j<M;j++)
    {
        Sp=0;
        for (i=0;i<N;i++)
        {
            Sp+=m[i][j];
        }
        if (Sp<0)
        {
            for (i=0;i<N;i++)
            {
                m[i][j]=-m[i][j];
            }
        }
    }
    for (i=0;i<N;i++)
        for (j=0;j<M;j++)
            S+=m[i][j];
    fprintf(fout,"%d\n",S);
    fclose(fin);fclose(fout);
    return 0;
}