#include <iostream>
#include <fstream>

using namespace std;

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

int walmart[1000041];
void starterup(int a){
    walmart[1] = 1;
    for(int i = 2; i <= a; i++){
        walmart[i] = i-1;
    }
}

long long sol = 1;
void rool(int a){
    starterup(a);
    for(int i = 2; i <= a; i++){
        sol += 2 * walmart[i];
        for(int j = i+i; j <= a; j += i){
            walmart[j] -= walmart[i];
        }
    }
}

int main()
{
    int a;
    fin >> a;
    
    rool(a);
    fout << sol;
    
    return 0;
}