#include <bits/stdc++.h>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");


int main()
{
long long unsigned n, i, j, c; c = 1;
vector <bool>A(n + 3, 1);
fin >> n;
for(i = 3; i <= n; i += 2)
{
  if(A[i] == 1)
  {
    ++c;
    for(j = 2; j <= n/i; ++j)
      A[i * j] = 0;
  }
}
fout << c;

return 0;
}