#include<stdio.h>
char v[2000000];
long int i,j,n,cont,d,k;
int main()
{FILE *f,*g;
f=fopen("ciur.in","r");
g=fopen("ciur.out","w");
      fscanf(f,"%ld",&n);
 i=2;
    while(i<=n)
{
  v[i]=1;
  i++;
}
 d=2;
 while(d<=n)  {
  if(v[i]==1)
    {cont++;
    for(j=i+i;j<=n;j+=i)
        v[j]=0;
        d++;
     }
               }
fprintf(g,"%ld",k);
fclose(f);
fclose(g); 
return 0;
}