fun readInt () =
  TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn

val () =
  case readInt () of
       SOME 1 => print "Hello World\n"
     | SOME 2 =>
         let
           val SOME a = readInt ()
           val SOME b = readInt ()
         in
           print (Int.toString (a + b) ^ "\n")
         end
