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: Accepted)

import java.util.*
import kotlin.math.floor

val sc = Scanner(System.`in`)

fun main(args: Array<String>) {

    val A = sc.nextLong().toDouble()
    val B = sc.nextLong().toDouble()
    val N = sc.nextLong().toDouble()

    val x = if(N < B - 1) N else B - 1
    val ans = floor(A * x / B) - A * floor(x / B)
    println(ans.toInt())
}