#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream f("ciur.in");
    ofstream g("ciur.out");
    int N, nr ;
    f>>N;
    int* vector;
    vector=(int *) calloc(N,sizeof(int));
    int i,j;
    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;
}