upari :: [Int] -> [[(Int, Int)]]
upari [] = []
upari [a, b] = [[(a, b)]]
upari (a:xa) = foldl ff [] [0..length(xa) - 1]
  where
    ff :: [[(Int, Int)]] -> Int -> [[(Int, Int)]]
    ff acc i = acc ++ map (\res -> (a, b):res) (upari(left ++ right))
      where
        (left, b:right) = splitAt i xa
        

main = mapM_ print (upari [1..6])