var
 n,d,i,c:longint;
 ok:boolean;
 f,g:text;
begin
 assign(f,'ciur.in');
 reset(f);
 readln(f,n);
 close(f);
 i:=2;
 while (i<=n) do
  begin
   ok:=true;
   d:=2;
   while (d<=i/d) and ok do
    if i mod d=0
     then
      begin
       ok:=false;
       break
      end
     else
      if d=2
       then
        d:=3
       else
        d:=d+2;
    if ok
     then
      c:=c+1;
    i:=i+1;
   end;
 assign(g,'ciur.out');
 rewrite(g);
 writeln(g,c);
 close(g);
end.