#include<iostream.h>
#include<fstream.h>
#include<math.h>
long int n;int i,j,k,a[2000000];
int main()
{
fstream f("ciur.in",ios::in);
fstream g("ciur.out",ios::out);
f>>n;
for(i=3;i<=n;i=i+2)
	a[i]=1;
for(i=3;i<=sqrt(n);i=i+2)
	if(a[i]==1) {k=(n-i)/i;j=2;while(j<=k+1) {a[i*j]=0;j=j+1;}}
	k=0;
for(i=3;i<=n;i=i+2)
if(a[i]==1)k++;
g<<k+1;
f.close();g.close();
return 0;
}