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#include <fstream>
using namespace std;
ifstream cin("submultimi.in");
ofstream cout("submultimi.out");
int main()
{
    int v[20][20]={0},vr[20][20]={0},m,n,s1=0,s2=0,st=0;
    cin>>n>>m;
    for(int i=1;i<=n;i++)
    {
        s1=0;
        s2=0;
        for(int j=1;j<=m;j++)
        {
            cin>>vr[i][j];
            if(vr[i][j]>0)
            {
                v[i][j] = 1;
            }
            else
            {
                v[i][j]=0;
            }
            if(v[i][j]==1)
            {
                s1 +=vr[i][j];
            }else
            {
                s2 += vr[i][j];
            }
        }
        if(s1<s2)
        {
            for(int j=1;j<=m;j++)
            {
                vr[i][j] = vr[i][j]*(-1);
                if(v[i][j]==1)
                {
                    v[i][j] = 0;
                }else
                {
                    v[i][j] = 1;
                }
            }
            
        }
    }
    for(int j=1;j<=m;j++)
    {
        s1=0;
        s2=0;
        for(int i=1;i<=n;i++)
        {
            if(v[i][j]==1)
            {
                s1 +=vr[i][j];
            }else
            {
                s2 += vr[i][j];
            }
        }
        if(s1<s2)
        {
            for(int i=1;i<=n;i++)
            {
                vr[i][j] = vr[i][j]*(-1);
                if(v[i][j]==1)
                {
                    v[i][j] = 0;
                }else
                {
                    v[i][j] = 1;
                }
            }
            
        }
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=1;j<=m;j++)
        {
            if(v[i][j]==1)
            {
                st += vr[i][j];
            }
        }
    }
    cout<<st;
}