#include<iostream>
#include<fstream>
using namespace std;
int n, i, j, p[1000001];
long long s;
int main ()
{
    ifstream fin ("fractii.in");
    ofstream fout ("fractii.out");
    fin>>n;
    for (i=1; i<=n; i++)
        p[i]=i-1;
    for (i=1; i<=n; i++)
        if (p[i]==i-1)
            for (j=2*i; j<=n; j+=i)
                p[j]-=p[i];
    for (i=1; i<=n; i++)
        s+=2*p[i];
    fout<<s+1;

}