/*Fractii*/
#include <fstream>
#define NMax 1000001
using namespace std;
int n;
long phi[NMax];

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