#include<bits/stdc++.h>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int n, sum, i, j;
vector<int> v(1000001);

void phi_1_to_n(int n)
{
    for(int i = 0; i <= n; i++)
        v[i] = i;

    for(int i = 2; i <= n; i++)
    {
        if(v[i] == i)
        {
            for(int j = i; j <= n; j += i)
                v[j] -= v[j] / i;
        }
    }
}

int main()
{
    fin>> n;
    phi_1_to_n(n);

    sum = 0;
    for(i = 1; i <= n; i++)
        sum += v[i];

    fout<< sum*2-1;
    return 0;
}