#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("flip.in");
ofstream fout("flip.out");
int main()
{
    int n,m,sm,sp,s = 0,mat[20][20];
    fin >> n >> m;
    for(int i = 1; i <= n; i++)
    {
        sm = 0;
        sp = 0;
        for(int j = 1; j <= m; j++)
        {
            fin >> mat[i][j];
            if(mat[i][j] < 0)sm = sm + mat[i][j];
            else sp = sp+ mat[i][j];
        }
        if(sm * (-1) > sp)
        {
            for(int j = 1; j <= m; j++)mat[i][j] = mat[i][j] * (-1);
        }
    }
    for(int j = 1; j <= m; j++)
    {
        sm = 0;
        sp = 0;
        for(int i = 1; i <= n; i++)
        {
            if(mat[i][j] < 0)sm+=mat[i][j];
            else sp+=mat[i][j];
        }
        if(sm * (-1) > sp)
        {
            for(int i = 1; i <= n; i++)mat[i][j] = mat[i][j] * (-1);
        }
    }

    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= m; j++)s+=mat[i][j];
    }
    fout << s;
}