#include <iostream>
#include <fstream>

using namespace std;

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

int n;
int ind[1000005];
bool ciur[1000005];
unsigned long long ans;

int main()
{
    fin >> n;
    for(int i = 2; i <= n; i++)
        ind[i] = i;
    for(int i = 2; i <= n; i++)
        if(!ciur[i])
            for(int j = i; j <= n; j += i)
                ind[j] = ind[j] * (i - 1) / i, ciur[j] = 1;
    for(int i = 2; i <= n; i++)
        ans += ind[i] * 2;
    fout << ans + 1;
    return 0;
}