#include<iostream>
#include<fstream>
using namespace std;
#define MAXN 2000001
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int phi[MAXN];

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