var f,g:text;
    a:array[2..2000000000]of boolean;
    i,j,b,n:longint;
begin
 assign(f,'ciur.in'); reset(f);
 assign(g,'ciur.out'); rewrite(g);
 readln(f,n);
 for i:=2 to n do
  if a[i]=false then begin
   a[i]:=true;
   inc(b);
   for j:=i+1 to n do
    if (j mod i)=0 then a[j]:=true;
  end;
 writeln(g,b);
 close(f);
 close(g);
end.