#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const int MAX=10e6+1;
int fi[MAX],n;
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)
       fi[i]=i;
       for(int i=1;i<=n;i++)
       if(fi[i]==i)
       for(int j=i;j<=n;j=j+i)
       fi[j]-=fi[j]/i;
       long long ans=-1;
       for(int i=1;i<=n;i++)
       ans=ans+2*fi[i];
       cout<<ans;
    return 0;
}