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) throws Exception {
        
        Scanner sc = new Scanner(System.in);
        String line1 = sc.nextLine();
        
        String[] array = line1.split(" ");
        
        long a = Long.parseLong(array[0]);
        long b = Long.parseLong(array[1]);
        long n = Long.parseLong(array[2]);
        
        double max = 0;
        double result = 0;
        for(int x = 0; x <= n; x++)
        {
            if(x >= 100000000)
            {
                break;
            }
            result = Math.floor((a * x) / b) - a * Math.floor(x / b);
            if(result > max)
            {
                max = result;
            }
        }
        
        System.out.println((int)max);
    }
}