
mc25.hs:9:46:
    Couldn't match expected type `a -> t0' with actual type `Int'
    Expected type: (a -> t0) -> [a] -> t1 (t2 a)
      Actual type: Int -> [a0] -> [a0]
    In the expression: take
    In a stmt of a monad comprehension: then group by x using take
