import Data.Ratio

(%%) :: Integral a => Ratio a -> Ratio a -> Ratio a
n %% d = (numerator n * denominator d) % (denominator n * numerator d)
 
main :: IO ()
main = do
    bs <- map read . words <$> getLine
    print $ solve bs

solve :: [Integer] -> Integer
solve [b1, b2, b3] = numerator $ r * toRational b3 + d
    where d = (b1 * b3 - b2 ^ 2) % (b1 - b2)
          r = -(d - toRational b2) %% toRational b1