--1
fib :: Integer -> Integer
fib 0 = 1
fib 1 = 1
fib n = fib (n-1) + fib (n-2)

--2
mdc :: Int -> Int -> Int
mdc x y | (x==y) = x
        | (x>y) = mdc (x-y) y
        | otherwise = mdc y x

--3 REVERSE
reverse2 :: [a] -> [a]
reverse2 [] = []
reverse2 (x:xs) = reverse2 xs ++ [x]


--4
unico :: [Integer] -> [Integer]
unico (x:xs) | elem x xs = unico (apaga x xs)
             | otherwise = x:unico xs

--APAGAR ELEMENTO LISTA
apaga:: Integer -> [Integer] -> [Integer]
apaga _ [] = []
apaga y (x:xs) | y == x = apaga y xs
               | otherwise = x:apaga y xs

unico2 l = [x | x<-l, length[y | y<-l, y==x]==1]