#include <iostream>
#include <cstdio>

using namespace std;

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

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

  return 0;
}