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.*

class Scanner(`in`: java.io.InputStream) {
    private val reader = java.io.BufferedReader(java.io.InputStreamReader(`in`))
    private var tokenizer: StringTokenizer? = null

    fun next(): String {
        if (tokenizer?.hasMoreTokens() != true) {
            tokenizer = StringTokenizer(reader.readLine())
        }
        return tokenizer!!.nextToken()
    }

    fun nextLine(): String {
        return if (tokenizer?.hasMoreTokens() != true) {
            reader.readLine()
        } else tokenizer!!.nextToken("\n")
    }
}

fun main(args: Array<String>) {
    val pw = java.io.PrintWriter(System.out)
    Problem.solve(Scanner(System.`in`), pw)
    pw.flush()
}

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object Problem {
    fun solve(sc: Scanner, pw: java.io.PrintWriter) {
        val A = sc.next().toLong()
        val B = sc.next().toLong()
        val N = sc.next().toLong()
        var x = B * (N / B) - 1
        if (x < 0) x = N
        val AxB = A * x / B
        val xB = x / B
        val ans = AxB - (A * xB)
        pw.println(ans)
    }
}