type Triplet = (N * N * N)

sumTripletList : List (N * N * N) -> N
sumTripletList [] = 0
sumTripletList ((n1, n2, n3) :: rest) = (n1 + n2 + n3 + (sumTripletList rest))

type Tree = Unit + (N * Tree * Tree)

sumTree : Tree -> N
sumTree (left _) = 0
sumTree (right (n, l, r)) = n + sumTree(l) + sumTree(r)