#include <bits/stdc++.h>
using namespace std;
ifstream fin ("fractii.in") ;
ofstream fout ("fractii.out") ;
long long n , i , j , a[1000005] ;
long long sum , nr = 1 ;
int main()
{
    fin >> n ;
    for ( i = 2 ; i <= n ; i ++ )
    {
        if ( a[i] == 0 )
        {
            for ( int j = i * 2 ; j <= n ; j += i )
                a[j] += j / i - 1 ;
        }
        a[i] ++ ;
    }
    for ( i = 2 ; i <= n ; i ++ )
        sum += a[i] * 2 - 1 ;
    nr = n * n ;
    fout << nr - sum ;

    return 0;
}