# include <stdio.h>
# include <math.h>
long int i,n,k;
int prim (int x)
{
int j;
for (j=2;j<=sqrt (x);j++)
if (x%j==0)
return 0;
return 1;
}
int main ()
{
freopen ("ciur.in","r",stdin);
freopen ("ciur.out","w",stdout);
scanf ("%li",&n);
for (i=3;i<=n;i++)
if (prim (i)==1)
k++;
printf ("%li",k+1);
return 0;
}