#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int n,a[1000001],i,j;
long long int s=1;

int main()
{
    fin >> n;
    for(i=1;i<=n;i++)
    {
        a[i]=i-1;
    }
    for(i=2;i<=n;i++)
    {
        s+=a[i]*2;
        for(j=2*i;j<=n;j+=i)
            a[j]-=a[i];
    }
    fout << s;
    return 0;
}