#include <bits/stdc++.h>
#define N 2000000

using namespace std;

ifstream f ("ciur.in");
ofstream g ("ciur.out");

int n;
//bitset < N / 2 + 1 > ciur;
char p[N / 2 / 8 + 1];

int main()
{
    int i , j , nr = 1;

    f >> n;

   for (i = 1; ((i * i) << 1) + (i << 1) <= n; i += 1) {
      if ((p[i >> 3] & (1 << (i & 7))) == 0) {
        for (j = ((i * i) << 1) + (i << 1); (j << 1) + 1 <= n; j += (i << 1) + 1) {
          p[j >> 3] |= (1 << (j & 7));
        }
      }
    }

    for (i = 1; 2 * i + 1 <= n; ++i)
         if ((p[i >> 3] & (1 << (i & 7))) == 0)
             nr++;


    g << nr;

    return 0;
}