#include <fstream>
#include <iostream>

using namespace std;
int a[1000005], n;

void Phi(int n)
{
    int i,j;
    for(i = 2; i<=n;i++)
        a[i]=i-1;
    for(i=2;i<=n; i++)
        for(j=i+i;j<=n;j=j+i)
            a[j]=a[j]-a[i];
}

int main()
{
    int i; long long S;
    ifstream fin ("fractii.in");
    ofstream fout ("fractii.out");

    Phi(1000000);

    fin >> n;
    S=1;

    for(i = 2; i<=n; i++)
        S = S + 2 *a[i];
    fout << S << "\n";

    fin.close();
    fout.close();

    return 0;
}