type tabel=array[2..2000000]of boolean;
var n,i,j,ciur:longint;
    t:tabel;
begin
 assign(input,'ciur.in');
 reset(input);
 read(n);
 close(input);

 for i:=2 to n do t[i]:=true;
 ciur :=0;
 for i:=2 to n do
  begin
   for j:=i+1 to n do
    if j mod i=0 then t[j]:=false;
  end;

  for i:=2 to n do if t[i] then ciur:=ciur+1;
  write(ciur);
end.