#include<iostream>
#include<fstream>

using namespace std;

int main () {
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long int n, i, j, nr=0;
fin>>n;
long int v[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*(i-1);
for (i=1; i<=n; i++)
        nr+=2*v[i];
fout<<nr-1;
return 0;

}