#include <fstream>
using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
int e[1000001];
int main()
{
    //int n,i,j;
    long long s=0;
    int i,j,n;
    in>>n;
    for(i=1;i<=n;i++)
        e[i]=i;
    for(i=2;i<=n;i++)
        if(e[i]==i)
            for(j=i;j<=n;j=i+j)
                e[j]=e[j]/i*(i-1);
    for(i=1;i<=n;i++)
    {
        s=s+e[i];
       // out<<i<<"i  "<<"s"<<s<<" ei"<<e[i]<<"\n";
    }
    out<<2*s-1;


    return 0;
}