#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int x[1000000],n,i,j;
long long numere;

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