#include<fstream>
 
using namespace std;
 
int main()
{
    int v[1000005];
    long long contor,i,j,n;
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f>>n;
    contor=0;
    for(i=2;i<=n;i++)
    v[i]=i-1;
    for(i=2;i<=n;i++)
    {
        contor=contor+v[i];
        for(j=i+i;j<=n;j=j+i)
        v[j]=v[j]-v[i];
    }
    contor=contor*2+1;
    g<<contor;
    f.close();
    g.close();
    return 0;
}