import Data.Map.Strict as Map

keyValuesToMap :: (Eq k, Ord k, Ord v) => [(k, v)] -> Map k [v]
keyValuesToMap x = keyValuesToMap_ x empty

keyValuesToMap_ :: (Eq k, Ord k, Ord v) => [(k, v)] -> Map k [v] -> Map k [v]
keyValuesToMap_ [] map = map
keyValuesToMap_ (x:xs) map = keyValuesToMap_ xs map_
    where
        (key, val) = x
        currVal = findWithDefault [] key map
        map_ = insert key (currVal ++ [val]) map

main = do
    print $ keyValuesToMap [(1, "one"), (2, "two"), (1, "uno")]