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 Scala (2.13.1) (judge verdict: Wrong Answer)

import java.util.Scanner

import scala.math.BigDecimal.RoundingMode

object Main extends App {
  val sc = new Scanner(System.in)
  val (a, b, n) = (sc.nextInt(), sc.nextLong(), sc.nextLong())

  val bDecimal = BigDecimal(b)
  println(floor(a * n / bDecimal) - a * floor(n / bDecimal).toLong)
  
  def floor(bd: BigDecimal) = bd.setScale(0, RoundingMode.FLOOR)
}