#include <iostream>
#include <fstream>

using namespace std;

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;
    cin >> a;
    
    rool(a);
    cout << sol;
    
    return 0;
}