import Control.Monad

main = do
  xys <- replicateM 3 $ liftM (map read . words) getLine
  let
      f z [x, y] = z `mod` y == x
      zs = filter (\z -> all (f z) xys) [1..1000000]
   in print $ case zs of
                (z:_) -> z
                otherwise -> (-1)