function Check(n: longint): string;
var
  i,k:longint;
begin
  for i:=1 to n do
if n mod i=0 then k:=k+1;
if k>2 then Check:='NO'
else Check:='YES';
end;
var
  a: integer;

begin
  readln(a);
  writeln(Check(a));
end.