5.3

program prog;
var
   a, b, s : longint;
   i, j : longint;
begin
  while (true) do begin
  Readln(a);
  b := 0;
  for i := a - 1 downto 2 do
    if (a mod i = 0) then begin
       b := 1;
       break;
    end;
  if (b = 0) then
    writeln('Yes')
  else
    writeln('No');
  end;
end.