#include <fstream>
#include <iostream>

int v[1000001];

using namespace std;
ifstream in ( "fractii.in" );
ofstream out ( "fractii.out" );

int main()
{
    int n, i, j, nr;

    in>>n;

    for ( i = 2; 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 * ( i - 1 );
            }
        }
    }
    nr = 0;
    for ( i = 2; i <= n; i++ ) {
        nr = nr + v[i];
    }
    out<<nr+n;


    return 0;
}