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';

  k := n-1;
  for i := 2 to n div 2 do
     for j :=  2 to n div i do
        begin
           if c[i*j] = '0' then
              k := k - 1;
           c[i*j] := '1';
        end;


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