#include <bits/stdc++.h>

using namespace std;

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

int n, sol;
int f[1000005];

int main(){
    fin >> n;
    for (int i=1; i<=n; i++){
        f[i] = i;
    }
    for (int i=2; i<=n; i++){
        if (f[i] == i){
            f[i]--;
            for (int j=2; j*i<=n; j++){
                f[j*i] = f[j*i] / i * (i - 1);
            }
        }
    }
    for (int i=2; i<=n; i++){
        sol += f[i];
    }
    fout << 2*sol + 1;
    return 0;
}