#include <fstream>
#include <bitset>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
int n,i,j,numere;
bitset <1415> a;
int main()
{
    in>>n;
    a[1]=1;
    for (i=2;i*i<=n;++i)
    {
        if (!a[i])
        {
            for (j=i;j<=n/i;++j)
                 a[j*i]=1;
        }
    }
    for (i=2;i<=n;++i)
         if (!a[i]) ++numere;
    out<<numere<<"\n";

}