A+BC

#include <bits/stdc++.h>

using namespace std;

​

#define ll long long

#define vll vector<ll>

#define rep(i, n) for (ll i = 0; i < n; ++i)

constexpr ll INF = (1ll << 60);

​

template <typename T>

inline bool chmin(T &a, T b) {

    if (a > b) {

        a = b;

        return 1;

    }

    return 0;

}

​

int main() {

    ll n,ans=0;

    cin>>n;

    vll a(n+1,INF); //a[x]... x = A*B となるA+Bの最小値

    //a[0]...a[N]を求める O(NlogN)

    rep(i,n+1){

        rep(j,n+1){

            if(i*j>n) break;

            chmin(a[i*j],i+j);

        }

    }

    //累積最小値を取る O(N)

    rep(i,n){

        chmin(a[i+1],a[i]+1);

        ans+=a[i+1];

    }

    cout<<ans<<endl;

}