#include <stdio.h>
int n;
int ciur(int n)
{
     int i,c,x[2000000],k,v;
     x[2]=2;
     c=2;
     k=1;
     v=1;
     for(i=2;i<=n;i++) x[i]=1;
     while(v==1)
     {
     v=0;
     for(i=c;i<=n;i+=c)
      x[i]=-1; 
     for(i=c;i<=n;i++)
      if (x[i]!=-1)
      {
       c=i;
       k++;
       v=1;
       break;
      }
     }
     return k;
}
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    printf("%d",ciur(n));
    return 0;
}