main :: IO ()                                                                                                              
main = do                                                                                                                  
  x <- getLine                                                                                                             
  case x of                                                                                                                
    "1" -> putStrLn "Hello World"                                                                                          
    "2" -> do                                                                                                              
      a <- (read <$> getLine) :: IO Int                                                                                    
      b <- (read <$> getLine) :: IO Int                                                                                    
      putStrLn $ show (a + b)