#include <iostream>
#include <fstream>

using namespace std;

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

long long n, k, v[1000010];
int i, j;

int main()
{

    f>>n;
    for (i=1;i<=n;i++)
        v[i]=i;

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