import Control.Applicative

main :: IO ()
main = solve <$> f >>= print
  where
    f = map read <$> words <$> getLine

solve :: [Int] -> Int
solve [k, a, b]
  | a <= b = if a >= k then 1 else -1
  | otherwise = let i = (k - b + a - b - 1) `div` (a - b) in max 1 (2 * i - 1)
