#include<bits/stdc++.h>

using namespace std;

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

int v[1000005],n;

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

int main()
{
    int i;
    long long sum;
    sum=1;
    Rezolvare(1000000);
    fin >> n;
    for(i=2;i<=n;i++)
        sum+=2*v[i];
    fout << sum << "\n" ;
    return 0;
}