#include <cstdio>

using namespace std;

int n,pm[140000];

inline int ciur()
{
    int i,j,nr=1;
    for (i=1;((i*i)<<1)+(i<<1)<=n;++i)
     if ((pm[i>>3]&(1<<(i&7)))==0)
     {
         for (j=((i*i)<<1)+(i<<1);(j<<1)+1<=n;j+=(i<<1)+1)
            pm[j>>3]|=(1<<(j&7));
     }

    for (i=1;2*i+1<=n;++i)
     if ((pm[i>>3]&(1<<(i&7)))==0)
      nr++;

   return nr;
}

int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);

    scanf("%d", &n);
    printf("%d\n", ciur());


    return 0;
}