program Ciurul;
var
  fl : text;
  c : array[1..200000000] of char;
  n, i, j, k : longint;
begin
  assign(fl,'ciur.in');
  reset(fl);
  readln(fl,n);
  close(fl);

  c[1] := '1';
  for i := 2 to n do
     c[i] := '0';

  for i := 2 to n div 2 do
     for j :=  2 to n div i do
        c[i*j] := '1';


  k := 0;
  for i := 1 to n do
     if c[i] = '0' then
        k := k + 1;

   assign(fl,'ciur.out');
   rewrite(fl);
   writeln(fl,k);
   close(fl);
end.