#include <stdio.h>     
char v[2000002];      
long n,c,i,j;       
int main()   
{        
freopen("ciur.in","r",stdin);      
freopen("ciur.out","w",stdout);      
     
scanf("%ld",&n);      
     
for(i=3;i<=n;i=i+2)      
   if(!v[i]&&i%2) {      
    c++;      
    for(j=3*i;j<=n;j=j+2*i)  v[j]=1;       
   }       
c++;     
printf("%ld\n",c);         
return 0;      
}