#include <bits/stdc++.h>
#define NMAX 1000001
using namespace std;

long long sol = 1;
int n, a[ NMAX ];

int main(){
    ifstream cin("fractii.in");
    ofstream cout("fractii.out");
     cin >> n;
    for (int i = 1; i <= n; i++)
        a[ i ] = i - 1;
    for (int i = 2; i <= n; i++)
        for (int j = 2 * i; j <= n; j += i)
          a[ j ] -= a[ i ];
    for (int i = 1; i <= n; i++)
      sol += 2 * a[ i ];
    cout << sol;
 return 0;
}