#include <iostream>
#include <fstream>
using namespace std;
ifstream f("flip.in");
ofstream g("flip.out");

int N,M,i,j,s=0,k,sn,sp;
int main()
{
       f>>N>>M;

 int a[N+1][M+1];

    for(i=1;i<=N;i++)
    for(j=1;j<=M;j++)

        f>>a[i][j];

////////////////////////////////////////////////////
    for(j=1;j<=M;j++)
    {
        sn=sp=0;
    for(i=1;i<=N;i++)

        if(a[i][j]>0)
        sp+=a[i][j];
        else
        sn+=a[i][j];
        sn*=-1;

        if(sn>sp)
            for(k=1;k<=N;k++)
            a[k][j]=a[k][j]*-1;
    }
    ////////////////////
       for(i=1;i<=N;i++)
    {
        sn=sp=0;
    for(j=1;j<=M;j++)

        if(a[i][j]>0)
        sp=sp+a[i][j];
        else
        sn=sn+a[i][j];
        sn=sn*-1;

        if(sn>sp)
            for(k=1;k<=M;k++)
            a[i][k]=a[i][k]*-1;
    }
//////////////////////////////////////////////////////////////////
     for(i=1;i<=N;i++)
         for(j=1;j<=M;j++)
            s=s+a[i][j];
g<<s;

    return 0;
}