#include <fstream>

using namespace std;
int nrp,n,i,j;
bool a[2000010];
ifstream f("ciur.in");
ofstream g("ciur.out");
int main()
{    f>>n;
    nrp=1;
    for (i=3;i<=2000002;i+=2)
      a[i]=1;
      for (i=3;i<=n;i+=2)
        for (j=2*i;j<=n;j+=i)
          a[j]=0;
      for (i=3;i<=n;i+=2)
      if (a[i]==1) nrp++;
      g<<nrp;
    return 0;
}