#include<bits/stdc++.h>
using namespace std;
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define dbg(x) cout << #x << '=' << x << '\n';
#define ll long long
#define sz size()
#define x first
#define y second
#define pi pair <int, int>
#define pii pair <int, pi>
#define vi vector <int>
const ll mod = 1e9 + 7;
int n, cnt[1000001];
bool pr[1000002];
ll ans;

int32_t main(){
    ios_base :: sync_with_stdio(0); cin.tie(); cout.tie();
    ifstream cin("fractii.in");
    ofstream cout("fractii.out");
    cin>>n;
    for(int i=1; i<=n; i++) cnt[i]=i;
    for(int i=2; i<=n; i+=2) cnt[i]/=2;
    for(int i=3; i<=n; i+=2){
        if(pr[i]==0){
            for(int j=i; j<=n; j+=i){
                pr[j]=1;
                cnt[j]/=i;
                cnt[j]*=(i-1);
            }
        }
    }
    for(int i=1; i<=n; i++) ans+=(1LL*cnt[i]);
    cout<<ans*2-1;
}