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

int main()
{
    long n,i,j;
    unsigned long long nr_fractii = 0LL;
    ifstream fin("fractii.in");
    fin>>n;
    fin.close();
    vector<long> sir(n+1);

    for(i = 2;i<=n;++i)
        sir[i]=i-1;
    for(i = 2;i<=n;++i)
    {
        nr_fractii += sir[i];
        for(j=i*i;j<=n;j+=i)
            sir[j]=sir[j]-sir[i];
    }
    ofstream fout("fractii.out");
    fout<<nr_fractii*2+1;
    fout.close();
    return 0;
}