import List
import System.Environment

-- Naive method
un :: [Rational]
un = unfoldr (\x -> Just (x, (x+2)/(x+1))) 1

-- Newton's method
vn :: [Rational]
vn = unfoldr (\x -> Just (x, x/2+1/x)) 1

main = do
    argv <- getArgs           -- () -> IO [String]
    let s = read (head argv)  -- [String] -> Int
      in (putStrLn . show) (vn!!s)    -- Int -> IO String