extendRow :: [Int] -> ([[Int]], Int) -> ([[Int]], Int)
extendRow row (seq, n) = ((row ++ [n']) : seq, n')
where n' = last row + n
evaluate :: Sequence -> Int
extendRow :: [Int] -> ([[Int]], Int) -> ([[Int]], Int)
extendRow row (seq, n) = ((row ++ [n']) : seq, n')
where n' = last row + n
evaluate :: Sequence -> Int