#include <bits/stdc++.h>

using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int a[1000005], n;
long long s = 1;
void Ciur(int n)
{
    int i, j;
    for(i = 2; i <= n; i++)
        a[i] = i - 1;
    for(i = 2; i <= n; i++)
        for(j = i + i; j <= n; j = i + j)
            a[j] = a[j] - a[i];

}
void Rezolva()
{
    int i;
    Ciur(1000005);
    fin >> n;
    for(i = 1; i <= n; i++)
        s += 2 * a[i];
    fout << s << "\n";
}
int main()
{
    Rezolva();
    fout.close();
    return 0;
}