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

int main()
{
    FILE* f;
    FILE* g;
    f=fopen("flip.in","r");
    g=fopen("flip.out","w");

    int t[16][16],N,M,s=0,s1;
    fscanf(f,"%d%d",&N,&M);
    for (int i=1;i<=N;i++)
    {
        s1=0;
        for (int j=1;j<=M;j++)
        {
            fscanf(f,"%d",&t[i][j]);
            s1=s1+t[i][j];
        }
        if (s1<0)
        {
            for (int k=1;k<=M;k++)
            {
                t[i][k]=t[i][k]*-1;
            }
        }
    }
    for (int m=1;m<=M;m++)
    {
        s1=0;
        for (int n=1;n<=N;n++)
        {
            s1=s1+t[n][m];
        }
        if (s1<0)
        {
           for (int k=1;k<=N;k++)
            {
                t[k][m]=t[k][m]*-1;
            }
        }
    }
    for (int y=1;y<=N;y++)
    {
        for (int z=1;z<=M;z++)
        {
            s=s+t[y][z];
        }
    }
    fprintf(g,"%d",s);

    fclose(f);
    fclose(g);

    return 0;
}