#include <stdio.h>
int i,j,a,m,n,v[30][30],S,s;
int main()
{
    FILE* flip1=fopen("flip.in","r");
    FILE* flip2=fopen("flip.out","w");
    fscanf(flip1,"%d%d",&n,&m);
    for(i=0;i<=n-1;i++)
        for(j=0;j<=m-1;j++)
            fscanf(flip1,"%d",&v[i][j]);
    for(i=0;i<=n-1;i++)
        {
            s=0;
            for(j=0;j<=m-1;j++)
                s+=v[i][j];
            if(s<=0)
                for(j=0;j<=m-1;j++)
                    v[i][j]*=(-1);
        }
    for(j=0;j<=m-1;j++)
        {
            s=0;
            for(i=0;i<=n-1;i++)
                s+=v[i][j];
            if(s<=0)
                for(i=0;i<=n-1;i++)
                    v[i][j]*=(-1);
        }
    for(i=0;i<=n-1;i++)
       for(j=0;j<=m-1;j++)
                S+=v[i][j];

    fprintf(flip2, "%d", S);
    fclose(flip1);
    fclose(flip2);
    return 0;
}