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: Accepted)

import scala.io.StdIn.readLine
import scala.io.StdIn.readInt

object Main extends App {
    val abn = readLine.split(" ").map(_.toLong)
    val a = abn(0)
    val b = abn(1)
    val n = abn(2)
    def f(a:Long,b:Long,x:Long): Long = {
        (a*x/b)-a*(x/b)
    }
    if(n>=b-1) print(f(a,b,b-1));
    else print(f(a,b,n));
}