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#include <iostream>
#include <fstream>

using namespace std;

ifstream fin("flip.in");
ofstream fout("flip.out");

int main()
{
    int n,m,a[10][10],s, i, j;
    
    fin>>n>>m;
    for(i = 0; i < n; i++)
    {
        for(j = 0; j < m; j++)
        {
            fin>>a[i][j];
        }
    }
    for(i = 0; i < n; i++)
    {
        s=0;
        for(j = 0; j < m; j++)
        {
            s = s + a[i][j];
        }
        if(s < 0)
        {
            for(j =0; j<m;j++)
            {
                a[i][j] = (-1)*a[i][j];
            }
        }
    }
    
     for(j = 0; j < m; j++)
    {
        s=0;
        for(i = 0; i < n; i++)
        {
            s = s + a[i][j];
        }
        if(s < 0)
        {
            for(i=0;i<n;i++)
            {
                a[i][j] = (-1)*a[i][j];
            }
        }
    }
    s = 0;
    for(i=0;i<n;i++)
    {
        for(j=0;j<m;j++)
        {
            s = s+a[i][j];
        }
    }
    fout<<s;

    return 0;
}