fib4 n =
        let f = ((1, 1), (1, 0)) :: Matrix
            fm = f^n
        in (snd . fst) fm
fib4 n =
        let f = ((1, 1), (1, 0)) :: Matrix
            fm = f^n
        in (snd . fst) fm
fib4 n =
        let f = ((1, 1), (1, 0)) :: Matrix
            fm = f^n
        in (snd . fst) fm