lookupTree 1 (Node (2, 'a') (Node (1, 'b') Leaf Leaf) (Node (3, 'c') Leaf Leaf))
lookupTree 2 (Node (2, 'a') (Node (1, 'b') Leaf Leaf) (Node (3, 'c') Leaf Leaf))
lookupTree 10 (Node (2, 'a') (Node (1, 'b') Leaf Leaf) (Node (3, 'c') Leaf Leaf))
