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: Time Limit Exceeded)

import java.util.*;

public class Main {

    public static void main(String[] args) {

        Scanner scan = new Scanner(System.in);
        long a = scan.nextLong();
        long b = scan.nextLong();
        long n = scan.nextLong();
        long max = 0;
		List<Long> listA = new ArrayList<Long>(); 

		for (long x=1; x<n+1; x++) {
			listA.add((long)((a*x)/b) - a*(long)(x/b));
        }

/*
		max = listA
      	.stream()
      	.mapToLong(v -> v)
      	.max().orElseThrow(NoSuchElementException::new);
*/

		Collections.sort(listA,  Collections.reverseOrder());

		System.out.println(listA.get(0));
	    scan.close();	
    }
}