#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream f("flip.in");
    ofstream g("flip.out");
    int i,j,a[32000][16],n,m;
    f>>n>>m;
    for(i=1;i<=n;i++)for(j=1;j<=m;j++)f>>a[i][j];

    for(i=1;i<=n;i++)
    {
        int s1=0,s2=0;
        for(j=1;j<=m;j++)
            if(a[i][j]>0)s1+=a[i][j];
            else s2+=-1*a[i][j];
        if(s2>s1)
            for(j=1;j<=m;j++)
                a[i][j]*=-1;
    }
    for(j=1;j<=m;j++)
    {
        int s1=0,s2=0;
        for(i=1;i<=n;i++)
            if(a[i][j]>0)s1+=a[i][j];
            else s2+=-1*a[i][j];
        if(s2>s1)
            for(i=1;i<=n;i++)
                a[i][j]*=-1;
    }
    int s1=0;
    for(i=1;i<=n;i++)for(j=1;j<=m;j++)s1+=a[i][j];
    g<<s1;
    return 0;
}