#include <iostream>
#include <math.h>
#include <numeric>
#include <vector>

const int MAXN = 50'000'000;

void solve()
{
    int n;
    std::cin >> n;

    std::vector<int> squarefree(n + 1);
    std::vector<bool> isPrime(n + 1, true);
    std::iota(squarefree.begin(), squarefree.end(), 0);

    isPrime[0] = isPrime[1] = false;
    for (int i = 2; i * i <= n; i++) {
        if (!isPrime[i]) {
            continue;
        }

        int k = i * i;
        for (int j = k; j * j <= n; j += i) {
            isPrime[j] = false;
        }
        for (int j = k; j <= n; j += k) {
            while (squarefree[j] % k == 0) {
                squarefree[j] /= k;
            }
        }
    }

    int res = 0;
    for (int i = 1; i <= n; i++) {
        res += (int) std::sqrt(n / squarefree[i]);
    }
    std::cout << res << std::endl;
}

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    solve();

    return 0;
}