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: Runtime Error)

import kotlin.math.floor

fun main(args: Array<String>) {

    val (A, B, N) = readInts()

    if(N < B - 1){
        println(f(A, B, N))
    }else{
        println(f(A, B,B - 1))
    }

}

fun f(A: Int, B: Int, X: Int): Int{
    val a = A.toDouble()
    val b = B.toDouble()
    val x = X.toDouble()
    return (floor(a * x / b) - floor(x / b) * a).toInt()
}


// #######################################################

fun readInt(): Int{
    return readLine()!!.toInt()
}

fun readInts(): Array<Int>{
    return readLine()!!.split(" ").map(String::toInt).toTypedArray()
}

fun readInts2(n: Int) : Pair<Array<Int>, Array<Int>>{
    val a = Array(n){0}
    val b = Array(n){0}
    for(i in 0 until n){
        val r = readInts()
        a[i] = r[0]
        b[i] = r[1]
    }
    return Pair(a, b)
}