#include <bits/stdc++.h>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n;
int phi[1000005];

int main()
{
  f>>n;
  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 res = 1;
  for(int i = 2;i <= n;++i)
    res += 2 * phi[i];
  g<<res;
}