#include <iostream>
#include <stdio.h>

using namespace std;

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


int n,m,v[105][105],i,j,sum;

int main()
{
    fscanf(f,"%d%d",&n,&m);
    for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
    fscanf(f,"%d",&v[i][j]);
    for(j=1;j<=m;j++)
    {
        sum=0;
        for(i=1;i<=n;i++)
        sum+=v[i][j];
        if(sum<sum*(-1))
        for(i=1;i<=n;i++) v[i][j]*=(-1);
    }
    for(i=1;i<=n;i++)
    {
        sum=0;
        for(j=1;j<=m;j++)
        sum+=v[i][j];
        if(sum<sum*(-1))
        for(j=1;j<=m;j++) v[i][j]*=(-1);
    }
    sum=0;
    for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
    sum+=v[i][j];
    fprintf(g,"%d",sum);


    fclose(g);
    return 0;
}