#include <iostream>
#include <cstdio>
using namespace std;

long long rez, n, impartit;
int posibile[1000005];


int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    cin >> n;
    for (int i=1; i<=n; ++i)
    {
        posibile[i]=i-1;
    }
    impartit=n/2;
    for (int i=2; i<=impartit; ++i)
    {
        for (int j=2*i; j<=n; j+=i)
        {
            posibile[j]-=posibile[i];
        }
    }
    for (int i=2; i<=n; ++i)
    {
        rez+=2*posibile[i];
    }
    rez++;
    cout << rez;
    return 0;
}