#include <stdio.h>
#include <stdbool.h>
long i,j,n,i1,m=3;
bool a[100000000];

int main()
{ freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
   scanf("%i",&n);
   n=30000;
    for(i=6;i<n;i+=6)
    {  for(i1=i-1;i1<=i+1;i1+=2)
        if(i1%5!=0&&a[i1]!=1)
      {  a[i1]=1;m++;
        for(j=i1;j<=n;j+=i1*6)
        a[j]=1;
        if(i1%6==5&&i1<=n/i1+1)
       for(j=i1*i1;j<=n;j+=i1*6)
       a[j]=1;
    }
    }
    printf("%i",m);
    return 0;
}