#include <fstream>
#include <algorithm>

using namespace std;

ifstream inf("fractii.in");
ofstream outf("fractii.out");

int n, euler[1000010];

long long sol=1;

int main()
{
    inf>>n;
    for(int i=1; i<=n; i++)
        euler[i]=i-1;

    for(int i=2; i<=n; i++)
    {
        sol+=2*euler[i];
        for(int j=2*i; j<=n; j+=i)
            euler[j]-=euler[i];
    }

    outf<<sol<<"\n";
    return 0;
}