#include <fstream>
#define ios ios_base::sync_with_stdio(false);
#define nmax 2000005

using namespace std;

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

int i,j,n,nr=1;
char v[nmax];

int main()
{
    ios;
    cin.tie(0);
    cout.tie(0);
    cin>>n;
    for (i=3;i<=n;i+=2){
        if (!v[i]){
            nr++;
            for (j=2*i;j<=n;j+=i) v[j]++;
        }
    }
    cout<<nr;
    return 0;
}