#include <iostream>
#include <fstream>
#define maxn 1000000
using namespace std;
long long phi[maxn];
int main()

{long long s;
int n,i,j;
fstream f("fractii.in",ios::in);
fstream g("fractii.out",ios::out);
f>>n;
for(i=1;i<=n;i++)
        phi[i]=i;

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


        s=1;
        for(i=2;i<=n;i++)
            s=s+phi[i]*2;
        g<<s;
        g.close();
        f.close();

        }