#include <bits/stdc++.h>
using namespace std;

bool is_SPRP(uint32_t n, uint32_t a) {
  uint32_t d = n - 1, s = 0;
  while ((d & 1) == 0) {
    ++s;
    d >>= 1;
  }
  uint64_t cur = 1, pw = d;
  while (pw) {
    if (pw & 1) {
      cur = (cur * a) % n;
    }
    a = ((uint64_t)a * a) % n;
    pw >>= 1;
  }
  if (cur == 1) {
    return true;
  }
  for (uint32_t r = 0; r < s; r++) {
    if (cur == n - 1) {
      return true;
    }
    cur = (cur * cur) % n;
  }
  return false;
}

bool is_prime(uint32_t x) {
  if (x <= 1) return false;
  if (x < 1ULL << 32) {
    uint32_t bases[] = {2, 7, 61};
    for (uint32_t i = 0; i < sizeof(bases) / sizeof(bases[0]); ++i) {
      if (x != bases[i] && !is_SPRP(x, bases[i])) {
        return false;
      }
    }
    return true;
  }
}

int p[1000000];

int main() {
  int n;
  for (int i = 0; i < 1000000; ++i) {
    p[i] = is_prime(i);
  }
  for (int i = 1; i < 1000000; ++i) {
    p[i] += p[i - 1];
  }
  while (cin >> n) {
    cout << p[n] << endl;
  }
}