#include <bits/stdc++.h>
//#include <atcoder/all>
//using namespace atcoder;
#define rep(i, n) for(ll i = 0; i < n; i++)
#define rep2(i, m, n) for(ll i = m; i <= n; i++)
#define rrep(i, m, n) for(ll i = m; i >= n; i--)
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define MAX(x) *max_element(all(x))
#define MIN(x) *min_element(all(x))
#define SZ(a) ((ll)(a).size())
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
const ll mod = 1000000007;
const int dx[4] = { -1, 1, 0, 0 };
const int dy[4] = { 0, 0, 1, -1 };
const int inf = 1e9 + 1;
const ll INF = 1e18 + 1;
const double pi = acos(-1);

using Graph = vector < vector <ll >>;

//typedef atcoder::modint1000000007 mint;
//typedef atcoder::modint998244353 mint;
//typedef modint mint_b;

int sc[50000010];

const int MAX_N = 10000;
vector<int> prime; // i.th prime
vector<int> first_prime(MAX_N + 1); // その数を最初に割り切る素数を格納　i = first_prime[i]ならiは素数(i≧2)

void sieve() {
    for (int i = 0; i <= MAX_N; i++) first_prime[i] = 1;
    first_prime[0] = first_prime[1] = 1;
    for (int i = 2; i <= MAX_N; i++) {
        if (first_prime[i] == 1) {
            prime.push_back(i);
            for (int j = i; j <= MAX_N; j += i) first_prime[j] = i;
        }
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n; cin >> n;
    sieve();
    rep2(i, 1, n) sc[i] = i;

    for (int i = 2; i * i <= n; i++) {
        if (first_prime[i] == i) {
            for (int j = i * i; j <= n; j += i * i) {
                while (sc[j] % (i * i) == 0) {
                    sc[j] /= i * i;
                }
            }
        }
    }
    ll res = 0;
    rep2(i, 1, n) {
        res += sqrt(n / sc[i]);
    }

    cout << res << endl;
}