#include<iostream>
#include<fstream>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int const NMax = 1000005;
int V[NMax];
int n;
long long sol;

void Solve()
{
    int i, j;

    for(i=1; i<=n; i++)
        V[i] = i;

    for(i=2; i<=n; i++)
        if(V[i] == i){
            for(j=2*i; j<=n; j+=i)
                V[j] -= V[j] / i;
            V[i]--;
        }

    for(i=1; i<=n; i++)
        sol += V[i];

    g<<sol * 2 - 1<<"\n";
}

int main()
{
    f>>n;
    Solve();
    return 0;
}