#include"bits/stdc++.h"
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 998244353
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

vector<int> V(50000010),cnt(50000010,0);

signed main(){
    int N;cin>>N;
    iota(begin(V),begin(V)+N+1,0);

    for(int i=2;i<=N;i++)if(V[i]==i){
        for(int j=i;j<=N;j+=i){
            int c=0;
            while(V[j]%i==0) c++,V[j]/=i;
            if(c&1) V[j]*=i;
        }
    }
    
    ll ans=0;
    for(int i=1;i<=N;i++){
        ans+=2ll*cnt[V[i]]+1;
        cnt[V[i]]+=1;
    }
    cout<<ans<<endl;
    return 0;
}