24-A.hs

data Road = Road { src :: Int 
                 , dst :: Int
                 , cost :: Int
                 } deriving (Eq)

main :: IO ()
main = interact func

func :: String -> String
func s = let ds = lines s
             n  = head ds
             rs = tail ds
         in show (func' (read n) (map toRoad rs))
            
toRoad :: String -> Road
toRoad s = let ws = words s in Road { src = read $ ws!!0
                                    , dst = read $ ws!!1
                                    , cost = read $ ws!!2
                                    }

func' :: Int -> [Road] -> Int
func' _ rs = if costOne < costAnother
             then costOne
             else costAnother
  where oc = ocf ++ oct
        ocf = connectFrom 1 rs
        oct = connectTo 1 rs
        costOne = cycleCost 1 (oc!!0) rs
        costAnother = cycleCost 1 (oc!!1) rs
        
cycleCost :: Int -> Road -> [Road] -> Int
cycleCost pos road rs = if nextPos == 1
                        then nowCost
                        else nowCost + cycleCost nextPos nextRoad rs   
  where nextRoad = head $ filter (\r -> r /= road) $ connected pos rs
        (nextPos, nowCost) = if src nextRoad == pos
                             then (dst nextRoad, 0)
                             else (src nextRoad, cost nextRoad)

connected :: Int -> [Road] -> [Road]
connected n rs = connectFrom n rs ++ connectTo n rs

connectFrom :: Int -> [Road] -> [Road]
connectFrom n rs = filter (\r -> src r == n) rs

connectTo :: Int -> [Road] -> [Road]
connectTo n rs = filter (\r -> dst r == n) rs