#include    <iostream>
#include    <fstream>
#include    <algorithm>
#define ll long long
using namespace std;

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

ll phi[1000010];
int n;
ll cnt;

int main()
{
    fin>>n;
    for(int i=2;i<=n;i++)
      phi[i]=i-1;
    for(int i=2;i<=n;i++)
       {
        cnt+=phi[i];
      for(int j=2*i;j<=n;j+=i)
      {
        phi[j]-=phi[i];
      }
       }
      fout<<2*cnt+1;
}