#include <fstream>

using namespace std;

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

int main()
{
    int n, i, j, sum=0;

    in>>n;

    int e[n+1];

    e[0]=e[1]=0;

    for(i=2; i<=n; ++i){
        e[i]=i;
    }
    for(i=2; i<=n; ++i){
        if(e[i]==i){
            for(j=i; j<=n; j+=i){
                e[j]=e[j]/i*(i-1);
            }
        }
        sum+=e[i];
    }

    out<<sum*2+1;;

    return 0;
}