#include <iostream>
#include <cstring>
#include <algorithm>
#define ll long long
using namespace std;

const int maxn=5e7+10;
int p[maxn];
ll cnt[maxn];

void init(){
    p[1]=1;
    for(int i=2;i<maxn;i++){
        if(p[i]==0) {
            for (int j = i; j < maxn; j += i) {
                p[j] = i;
            }
        }
    }
}


int main(){
    ios::sync_with_stdio(false);
    init();

    int N;cin>>N;

    ll ans=0;
    for(int x=1;x<=N;x++){
        ans+=1;//ans+=(x,x)

        int K=x;
        int hash=1;
        while(K!=1){
            if(hash%p[K]==0){
                hash/=p[K];
            }else{
                hash*=p[K];
            }
            K/=p[K];
        }

        ans+=cnt[hash]*2;
        cnt[hash]+=1;
    }
    cout<<ans<<endl;
    return 0;
}