#include <iostream>
#include <fstream>

using namespace std;

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

long long n,d,v[200000000],i,j,Q;

int main()
{
    in>>n;
    for (i=1;i<=n;i++) v[i]=i;
    for (d=2;d*d<=n;d++)
    {
        for (j=2;j<=n;j++)
            if (v[j]%d==0 && v[j]!=d) v[j]=0;
    }
    for (i=2;i<=n;i++)
    {
        if (v[i]!=0)
        {
            Q++;
            cerr<<v[i]<<" ";
        }
    }
    out<<Q;
    return 0;
}