//#include<iostream>
#include<fstream>
using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");

int i,j,n,phi[1000002],s;

int main()
{
    cin>>n;
    for(i=1;i<=n;i++){
        phi[i]=i;
    }
    for(i=2;i<=n;i++){
        if(phi[i]==i){
            for(j=i;j<=n;j+=i){
                phi[j]/=i;
                phi[j]*=(i-1);
            }
        }
    }
    for(i=2;i<=n;i++){
        s+=phi[i];
    }
    cout<<2*s+1;
}