#include<fstream>
using namespace std;
long long max1=0;
int n,i,j,nr[1000001];
int main()
{    ifstream f("fractii.in");
    ofstream g("fractii.out");
f>>n;
    for(i=2;i<=n;i++)
            nr[i]=i-1;
        for(i=2;i<=n;i++)
    {        max1+=nr[i];
            for(j=2*i;j<=n;j+=i)
            nr[j]-=nr[i];    }
    max1=max1*2+1;
        g<<max1;
            return 0;
            }