#include <fstream>

using namespace std;
ifstream in ("fractii.in");
ofstream out("fractii.out");
int e[1000005];
int main()
{
    int n,j,i;
    long long s=0;
    in>>n;
    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=j+i)
                e[j]=e[j]/i*(i-1);

        }
    }
    for(i=2;i<=n;i++)
        s=s+e[i];


    out<<2*s+1;
    return 0;
}