main :: IO ()
main = interact $ show . solve . map read . words

splitEvery2 :: [Int] -> [[Int]]
splitEvery2 = takeWhile (not . null) . map (take 2) . iterate (drop 2)

solve :: [Int] -> Int
solve (n:m:xs) = foldl (\n -> \t -> if head t == n then last t else if last t == n then head t else n) n ys
    where
        ys = splitEvery2 xs