#include <fstream>
#include <algorithm>
using namespace std;

int n, i,nr,p[2000001],j;
bool ok;

ifstream fin("ciur.in");
ofstream fout("ciur.out");

int main ()
{
    fin >> n;

    for(i = 3; i <= n;i+=2)
        if(!p[i])
            for(j = i + i; j <= n; j += i)
                p[j] = 1;


    for(i = 2; i <= n; ++i)
        if(!p[i] && i%2)
            ++nr;

    fout << nr + 1;

    return 0;
}