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)

fun main() {
    val (a, b, n) = readLine()!!.split(" ").map(String::toLong)

    fun calc(x: Long) = (x * a / b) - a * (x / b)
    val result = when {
        a > b -> {
            (n downTo b).map { calc(it) }.max()
        }
        a < b -> {
            ((1..b).map { calc(it) } + (n downTo b).map { calc(it) }).max()
        }
        else -> 0
    }
    println(result)
}