main = do
  [a, b, c] <- map read . words <$> getLine
  print (solve a b c)

solve :: Integer -> Integer -> Integer -> Integer
solve a b c = f 0 (10^20)
  where
    f :: Integer -> Integer -> Integer
    f ng ok
      | ok - ng == 1 = ok
      | otherwise = let mid = div (ok + ng) 2
                        cost = mid + (b - 1) * div mid a
                    in if cost >= c
                         then f ng mid
                         else f mid ok