#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const int maxn = 1000005;
int rem[maxn];
int main()
{
    int n;
    in >> n;
    for(int i = 1; i < maxn; i++)
        rem[i] = i - 1;
    for(int i = 2; i < maxn; i++)
        for(int j = i + i; j < maxn; j = j + i)
            rem[j] = rem[j] - rem[i];
    long long s = 1;
    for(int i = 1; i <= n; i++)
        s = s + rem[i] * 2;
    out << s << "\n";
    return 0;
}