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 Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)


import java.util.Scanner;

public class Main {

	static long mod = 1000000007;

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		String[] t = sc.nextLine().split(" ");
		long a = Long.parseLong(t[0]);
		long b = Long.parseLong(t[1]);
		long c = Long.parseLong(t[2]);

		long ans = 0;

		double d = Math.floorDiv(a, b) - a * Math.floorDiv(1, b);


			ans = (long) Math.floor(a * c / b) - a * Math.floorDiv(c, b);
			ans = Math.max(ans, (long) Math.floor(a * 1 / b) - a * Math.floorDiv(1, b));
			ans = Math.max(ans, (long) Math.floor(a * 0 / b) - a * Math.floorDiv(0, b));

		System.out.println(ans);
	}
}