#include <fstream>
#include <iostream>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
long a[51][51];
int n,m,i,j,s,x,y,maxim,maxim1;
int main()
{
    fin>>n>>m;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            fin>>a[i][j];
    for(i=1;i<=n;i++)
    {
        s = 0;
        for(j=1;j<=m;j++)
        {
            if(a[i][j] < 0)
                s+=a[i][j];
        }
        if(s<maxim)
        {
            maxim = s;
            x = i;
        }
    }
    ///fout<<x;--este bine
    for(j=1;j<=m;j++)
    {
        s = 0;
        for(i=1;i<=n;i++)
            if(a[i][j]<0)
                s+=a[i][j];
        if(s<maxim1)
        {
            maxim1 = s;
            y = j;
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=1;j<=m;j++)
        {
                if(i == x)
                    a[i][j] = a[i][j]*(-1);
                if(j == y)
                    a[i][j] = a[i][j]*(-1);
        }
    }
    s = 0;
    for(i=1;i<=n;i++)
        for(j=1;j<=m;j++)
            s+=a[i][j];
    fout<<s;
    return 0;
}