#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h> 
using namespace std;
using ll=long long;
using P=pair<ll,ll>;
template<class T> using V=vector<T>; 
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
const ll inf=(1e18);
//const ll mod=998244353;
const ll mod=1000000007;
const vector<int> dy={-1,0,1,0},dx={0,-1,0,1};
ll GCD(ll a,ll b) {return b ? GCD(b,a%b):a;}
ll LCM(ll c,ll d){return c/GCD(c,d)*d;}
struct __INIT{__INIT(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(20);}} __init;
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1; } return 0; }
template<class T>void debag(const vector<T> &a){cerr<<"debag :";for(auto v:a)cerr<<v<<" ";cerr<<"\n";}
template<class T>void print(const vector<T> &a){for(auto v:a)cout<<v<<" ";cout<<"\n";}
bool used[50000005]={};
ll cnt[50000005]={};
V<int> val;
void make(int num){
    val.resize(num+1,1);
    val[0]=0;
    iota(all(val),0);
    for(ll i=2;i*i<=num;i++){
          if(used[i*i])continue;
          used[i*i]=true;
          for(ll j=i*i;j<=num;j+=i*i){
                while(val[j]%(i*i)==0){
                      val[j]/=(i*i);
                }
          }
    }
}
int main(){
      ll n;
      cin>>n;
      make(n);
      ll ans=n;
     for(int i=1;i<=n;i++){
           ans+=(cnt[val[i]]++)*2;
     }
      cout<<ans<<"\n";
}