app/cses1083.hs

   1 main :: IO ()
   2 main = do
   3   line1 <- getLine
   4   let numCount = read line1
   5   line2 <- getLine
   6   let nums = map read $ words line2
   7   print $ solve numCount nums
   8
   9 solve :: Int -> [Int] -> Int
  10 solve numCount nums = expected - actual
  11   where expected = (numCount * (numCount + 1)) `div` 2
  12         actual = sum nums