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.*

fun main(args: Array<String>) {
    val scanner = Scanner(System.`in`)
    val a = scanner.nextLong()
    val b = scanner.nextLong()
    val n = scanner.nextLong()
    if(b>n){
        println(Math.floor((a*n/b.toDouble())).toLong())
    }
    else if(b===n){
        println(Math.floor((a*(n-1)/b.toDouble())).toLong())
    }
    else{
        println((Math.floor((a*n/b.toDouble())).toLong())-(a*Math.floor((n/b.toDouble())).toLong()))
    }
}