#include <fstream>
#include <iostream>

std::ifstream input("fractii.in");
std::ofstream output("fractii.out");

long phi[1000001];
int main(){
    
    int n;
    long sum = 0;

    input >> n;
    for (int i = 1; i <= n; ++i){ 
        phi[i] = i-1;
    }

    for (int i = 2; i <= n; ++i){
        sum += phi[i];
        for (int j = 2*i; j <= n; j += i)
            phi[j] -= phi[i];
    }
    output << 2 * sum + 1 << '\n';
    input.close();
    output.close();
    return 0;
 
}