program ciur;
type    tabel=array [0..2000005] of boolean;
var     a:tabel;
        n,x,i,j:longint;
        f,g:text;
begin
  assign(f,'ciur.in'); assign(g,'ciur.out');
  reset(f); rewrite(g);
  readln(f,n);
  for i:=2 to n do
    if not a[i] then
      for j:=2 to n div i do
        a[i*j]:=true;
  a[1]:=true;
  for i:=2 to n do
    if not a[i] then x:=x+1;
  writeln(f,x);
  close(f); close(g);
end.