#include <iostream>
#include <fstream>

using namespace std;
ifstream f("date.in");
ofstream g("date.out");

int main()
{
    int n,m,a[50][50],l[50],c[50];
    f>>n>>m;
    for (int i=1;i<=n;i++)
        for (int j=1;j<=m;j++)
            f>>a[i][j];
    for (int i=1;i<=n;i++)
    {
        int s=0;
        for (int j=1;j<=m;j++)
            s=s+a[i][j];
        l[i]=s;
    }
    for (int j=1;j<=m;j++)
    {
        int s=0;
        for (int i=1;i<=n;i++)
            s=s+a[i][j];
        c[j]=s;
    }
    for (int i=1;i<=n;i++)
    {
        if (l[i]<0)
            for (int d=1;d<=m;d++)
                a[i][d]=a[i][d]*(-1);
    }
    for (int j=1;j<=m;j++)
    {
        if (c[j]<0)
            for (int s=1;s<=n;s++)
                a[s][j]=a[s][j]*(-1);
    }
    int i,j,s=0;
    for (i=1;i<=n;i++)
        for (j=1;j<=m;j++)
            s=s+a[i][j];
    g<<s;
    return 0;
}