#include <iostream>
#include <fstream>
using namespace std;
int v[1000000],i,j;
long long x=0,n;
int main()
{
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    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+=i)
                v[j]-=v[j]/i;
    for (i=1;i<=n;i++)
    {
        x=x+v[i];
    }
    g<<x*2-1;
    return 0;
}