#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    int N, nr ;
    f>>N;
    char vector[2000001];
    int i,j;
    for (i=0;i<N;i++)
    vector[i]='0';
    vector[0] = '1'; 
    nr = 1;
    for (i = 1; i*i <= N; i++)
    {
        if ( vector[i] == '1') continue;  // e verificat ca i+1 nu e prim
        else 
        for ( j =2*(i+1)-1; j < N ; j=j+i+1)
        {
            if ( vector[j] == '0') {  // nu e verificat si nu e prim
                 vector[j] = '1';
                 nr++;
               } 
        }
    }
    g<<N-nr;
    f.close();
    g.close();
    return 0;
}