#include<stdio.h>

    int main()
    {   
        int a[17][17];
        int m,n, i,j;
        int s, sp;
        FILE *in, *out;
        
        in=fopen("flip.in", "r");
        out=fopen("flip.out", "w");
        
        fscanf(in, "%d %d", &n, &m);
        for (i=1; i<=n; i++)
        for (j=1; j<=m; j++)
            fscanf(in, "%d", &a[i][j]);
            
        for (i=1; i<=n; i++)
        {
            s=0; sp=0;
            for (j=1; j<=m; j++)
            {   
                s+=a[i][j];
                sp=sp-a[i][j];
                if (sp>s)
                {
                    for (j=1; j<=m; j++)
                        a[i][j]=-a[i][j];
                }
            }
        }
                
        for (j=1; j<=m; j++)
        {
                s=0; sp=0;
                for (i=1; i<=n; i++)
                {
                    s+=a[i][j];
                    sp=sp-a[i][j];
                    if (sp>s)
                    {   
                        for (i=1; i<=m; i++)
                            a[i][j]=-a[i][j];
                    }
                }
        }
        
        s=0;
        for (i=1; i<=n; i++)
        for (j=1; j<=m; j++)
            s+=a[i][j];
            
        fprintf(out, "%d", s);
        
        fcloseall();
        return 0;                           
    }