#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
long long table[50000007];
bool is_prime[50000007];

//エラトステネスの篩(素数の数を返している)
//11→2,3,5,7,11
int sieve(long long  n) {
	int p = 0;
	is_prime[0] = false;
	is_prime[1] = false;
	for (int m = 2; m <= sqrt(n); ++m) {//初期化
		is_prime[m] = true;
	}

	for (int m = 2; m <= sqrt(n); ++m) {
		if (is_prime[m]) {
			++p;
			//素数なら。
			long long now = m * m;
			while (now <= n) {
				for (long long i = now; i <= n; i += now) {
					table[i] /= (m*m);
				}
				now *= m * m;
			}

			for (int l = 2 * m; l <= sqrt(n); l += m) is_prime[l] = false;
		}
	}
	return p;
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int n; cin >> n;
	rep(i, n + 1)table[i] = i;
	sieve(n);
	long long ans = 0;
	rep2(i, 1, n + 1) {
		ans += sqrt(n / table[i]);
	}
	cout << ans << endl;
	return 0;
}