#include <fstream>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int v[1000002];

int main()
{
    long long sol=0;

    int n;
    fin >> n;

    for (int i=1;i<=1000002;i++)
        v[i]=i;

    for (int i=2;i<=n;i++)
        if (v[i]==i)
            for (int j=i;j<=n;j+=i)
                v[j]-=v[j]/i;

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

    fout << 2*sol-1;

    return 0;
}