#include <fstream>
#include <bitset>


using namespace std;
bitset<200001>a;
int main()
{
    ifstream fin("ciur.in");
    ofstream fout("ciur.out");
    int i, j, k, n;
    fin>>n;
    k=1;
    for(i=4;i<=n;i=i+2) a[i]=1;
    for(i=3;i*i<=n;i=i+2)
    {
       if(a[i]==0)
       {
          for(j=i*i;j<=n;j=j+2*i) a[j]=1;
       }
    }
    for(i=3;i<=n;i=i+2)
    {
        if(a[i]==0) k++;
    }
    fout<<k;
    fin.close();
    fout.close();
    return 0;
}