#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

signed main() {
  freopen("fractii.in","r",stdin);
  freopen("fractii.out","w",stdout);
  int n;
  cin>>n;
  vector<int> phi(n+1);
  iota(phi.begin(),phi.end(),0);
  ll s=0;
  for (int i=2;i<=n;i++) {
    if(phi[i]==i){
      for(int j=i;j<=n;j+=i){
        phi[j]/=i;
        phi[j]*=(i-1);
      }
    }
    s+=phi[i];
  }
  cout<<2*s+1<<"\n";
  return 0;
}