TL solution for http://codeforces.com/contest/796/problem/B?locale=en

find_bone.hs

import System.IO
import Control.Monad
import Control.Applicative
import Data.List 
import qualified Data.Set as S

parseInt :: String -> Int
parseInt x = read x

solve :: Int -> [(Int,Int)] -> S.Set Int -> Int
solve x [] holes = x
solve x ((a,b):op) holes | S.member x holes = x
                         | x == a = if (S.member b holes) then b else solve b op holls
                         | x == b = if (S.member a holes) then a else solve a op holls
                         | otherwise = solve x op holls

main :: IO ()
main = do
    s0 <- getLine
    let n = parseInt ((words s0)!!0)
    let m = parseInt ((words s0)!!1)
    let k = parseInt ((words s0)!!2)
    s1 <- getLine
    let holes = S.fromList $ map parseInt (words s1)
    s3 <- replicateM k getLine
    let ops = map (\s -> let ss=words s in ((parseInt $ head ss),(parseInt $ ss!!1))) s3
    putStrLn $ show $ solve 1 ops holes

    return ()