#include <iostream>
#include <deque>
#include <fstream>
#include <bitset>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
constexpr int nmax = 2000001;
bitset<nmax> ciur;
void genciur()
{
    ciur[1] = ciur[0] = 1;
    for ( int i = 4; i < nmax; i+=2 )
        ciur[i] = 1;
    for ( int i = 3; i * i <= nmax; i += 2 )
       if ( ciur[i] == 0 )
        for ( int j = i * i; j <= nmax; j+=2*i)
          ciur[j] = 1;

}
int main()
{
    genciur();
    int n, r = 0;
    in >> n;
    for ( int i = 1; i <= n; ++i )
        if(!ciur[i])
          r++;
    out << r;

    return 0;
}