/*
   Keep It Simple!
*/

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

ifstream fin ("fractii.in");
ofstream fout ("fractii.out");

const int kMax_N = 1000005;

int dp [kMax_N], N;
long long rez;

int main () {
   fin >> N;
   rez = 1;
   for (int i = 2; i <= N; ++i) {
      dp[i] += (i-1);
      rez += 2*dp[i];
         for (int j = i + i; j <= N; j += i)
            dp[j] -= dp[i];
   }
   fout << rez << '\n';
}