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 Kotlin (1.3.71) (judge verdict: Wrong Answer)

import java.util.*

object MainKt {
    @JvmStatic
    fun main(args: Array<String>) {
        val scanner = Scanner(System.`in`)
        val a: Long
        val b: Long
        val n: Long
        a = scanner.next().toLong()
        b = scanner.next().toLong()
        n = scanner.next().toLong()
        var current: Long
        var max: Long = -1
        var count = 0
        for (x in n downTo 0) {
            current = a * x / b - a * (x / b)
            if (max <= current) {
                max = current
            }
            if (current <= max && current != 0L) {
                count++
                if (count <= 100) {
                    break
                }
            }
        }
        println(max)
    }
}