type vect= array [1..200] of longint;
 var v:vect; n,i,j,nr:longint;   f,g:text;
  begin
 assign(f,'ciur.in');reset(f);
  assign(g,'ciur.out');rewrite(g);
  read(f,n);
  close(f);
   for i:= 2 to n do
    v[i]:=i;
     nr:=0; v[1]:=0;
     for i:=2 to n do
      if v[i]<>0 then
       begin
        for j:=2 to n div i do
         v[i*j]:=0;
         inc(nr);
         end;
         write(g,nr);
         close(g);

       end.