#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in") ;
ofstream g("fractii.out") ;
int main()
{

    int n, a[1000002], i, j;
long long sol;

    f>>n;
    for(i=2;i<=n;i++)
                     a[i]=i-1;
    for(i=2;i<=n;i++)
{       sol=sol+a[i];
        for(j=i+i;j<=n;j+=i)
            a[j]=a[j]-a[i];}
g<<2*sol+1<<"\n";


    return 0;
}