#include <iostream>
#include <fstream>
using namespace std;

const int N = 1000001;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int a[N],n;
long long sol=1;

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