#include <iostream>
#include <fstream>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int fi[1000001];
int main()
{
    long long int s = 1;
    int n;
    fin >> n;
    fi[1] = 1;
    for(int i = 2; i<=n; i++) fi[i] = i-1;
    for(int i = 2; i <= n/2; i++)
    {
        for(int j = i + i; j <= n; j+=i)
        {
            fi[j] = fi[j] - fi[i];
        }

    }
    for(int i = 2; i <= n; i++)s+=fi[i] * 2;
    fout<<s;
    return 0;
}