#include <iostream>
#include <cstdio>

using namespace std;

const int NMAX = 2000000;
const int BASE = 64;

long long ciur[NMAX / BASE + 1];

int main() {
  freopen("ciur.in", "r", stdin);
  freopen("ciur.out", "w", stdout);
  int n, ans = 1;

  scanf("%d", &n);

  for(int i = 3; i <= n; i += 2)
    if(!( ciur[i / BASE] & ((long long)1 << (i % BASE)) )) {
      ans++;
      for(int j = 2 * i; j <= n; j += i)
        ciur[j / BASE] |= ((long long)1 << (j % BASE));
    }
  printf("%d", ans);

  return 0;
}