#include <bits/stdc++.h>
 
using namespace std;
 
ifstream f("fractii.in");
ofstream g("fractii.out");
 
int phi[1000007];
long long sum;
int n;
 
int main(){
 
    f >> n;
    sum = 1;
    
    for(int i = 2;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];
    }
 
    g << 2 * sum - 1;
 
}