#include <bits/stdc++.h>
#define ll long long
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
const int N = 1e6+5;
int n;
int euler(int x){
    int ans = x;
    for(int p = 2; p*p <=x; p++){
        if(x % p == 0){
            while(x % p == 0) x/=p;
            ans -= ans / p;
        }
    }
    if(x > 1) ans -= ans/x;
    return ans;
}
int main(){
    fin >> n;
    ll sol = 1;
    for(int i = 2; i<=n; i++){
        sol += 2*euler(i);
    }
    fout << sol;
    return 0;
}