#include <stdio.h>
#include <stdbool.h>
#define MAXSIZE 2000002

bool a[MAXSIZE];
void markup(bool a[],long long i, long long i11,long n)
{  long long j,j2;
    for( j =i11+i; j<= n; j += i11 )
                {
                    a[j]=true;}
         for(j2 = i*i;j2 <= n;j2 += i11 )
                       {
                        a[j2]=true;
                        }
}
void markdown(bool a[],long long i, long long i22,long n)
{
    long long j;

     for(j =i*i ; j <= n ; j += i22)
                a[j]=true;
}
int sieve(long n)
{
    long p,i,m=2;
    p=n/7;
    for( i= 6 ; i <=p ; i += 6)
    {
          if(! a [ i-1 ])
          {

           m++;
            markup(a,i-1,(i-1)*6,n+2);
          }
        if(! a [ i+1 ]){ m++;
           markdown(a,i+1,(i+1)*6,n+2);
        }

        }
 for(;i<n;i+=6,m+=!a[i+1]+!a[i-1]);


   if(n%6==0)
     return m+!a[n-1];
    else
      if((n+1)%6==0)
      return m+!a[n];
       return m;


}
int main()
{
    int n;
    //freopen("ciur.in","r",stdin);
    //freopen("ciur.out","w",stdout);
    //scanf("%i",&n);
    n=17;
    printf("%i",sieve(n));

     return 0;
}