#include <fstream>
#include <iostream>
using namespace std;
int a[1000005];

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

void Phi(int 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=j+i)
            a[j]=a[j]-a[i];
}

int main()
{
    int i,j,n;
    long long S=1;
    Phi(1000000);
    fin>>n;
    for(i=2;i<=n;i++)
        S=S+2*a[i];
    fout<<S<<"\n";
    fin.close();
    fout.close();

    return 0;
}