#include <iostream>
#include <fstream>

using namespace std;

int main() {
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    int n;
    int v[1000000];
    long total=1;
    in>>n;

    for(int i=1;i<=n;i++)
        v[i] = i-1;

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

    out<<total;
    in.close();
    out.close();
    return 0;
}