Problem:
Score : 400 points

Problem Statement

Given are integers A, B, and N.

Find the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N.

Here floor(t) denotes the greatest integer not greater than the real number t.

Constraints

1 ≤ A ≤ 10^{6}

1 ≤ B ≤ 10^{12}

1 ≤ N ≤ 10^{12}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B N

Output

Print the maximum possible value of floor(Ax/B) - A × floor(x/B) for a non-negative integer x not greater than N, as an integer.

Sample Input 1

5 7 4

Sample Output 1

2

When x=3, floor(Ax/B)-A×floor(x/B) = floor(15/7) - 5×floor(3/7) = 2. This is the maximum value possible.

Sample Input 2

11 10 9

Sample Output 2

9

Solution in Haskell (GHC 8.8.3) (judge verdict: Wrong Answer)

toInt x = read x :: Int
toFloat x = read x :: Float

newfloor :: Float -> Float -> Float -> Float
newfloor a b n 
     | n < b     = (fromIntegral (floor anb))
     | otherwise = (fromIntegral (floor amb)) - (a * fromIntegral (floor mb))
     where
          anb = a * nb
          amb = a * mb
          nb = n / b
          mb = (b-1) / b

main = do
     abn <- map toInt . words <$> getLine
     let a = fromIntegral $ head abn
         b = fromIntegral $ abn !! 1
         n = fromIntegral $ last abn
     print $ floor $ newfloor a b n