#include <iostream>
#include <fstream>
using namespace std;

int main()
{   int n,m,a[100][100],i,j,s1,s2,s=0;
ifstream f("flip.in");
ofstream g("flip.out");
f>>n>>m;
for(i=1;i<=n;i++)
    for(j=1;j<=m;j++)
        f>>a[i][j];

for(i=1,s1=0,s2=0;i<=n;s1=0,s2=0,i++)
    {for(j=1;j<=n;j++)
        if(a[i][j]>=0)
            s1=s1+a[i][j];
        else
            s2=s2+(-a[i][j]);
    if(s2>s1)
        for(j=1;j<=m;j++)
            a[i][j]=a[i][j]*(-1);
    }
for(j=1,s1=0,s2=0;j<=m;s1=0,s2=0,j++)
    {for(i=1;i<=n;i++)
        if(a[i][j]>=0)
            s1=s1+a[i][j];
        else
            s2=s2+(-a[i][j]);
    if(s2>s1)
        for(i=1;i<=n;i++)
            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]+s;
g<<s;
    return 0;
}