#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int N,phi[1000001];
long long s;
int main(){
   cin>>N;
   //daca i e prim phi[i]=phi=i-1
   for (int i = 1; i <= N; ++i)
    phi[i] = i-1;
    for (int i = 2; i <= N; ++i)
    for (int j = 2*i; j <= N; j += i)
                      phi[j] -= phi[i];
		   for(int i=2;i<=N;i++)
		                 s+=phi[i];
		cout<<2*s+1;
   return 0;
}