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: Runtime Error)

import java.util.Scanner;

public class Main {
	public static void main(String args[]){
		Scanner sc = new Scanner(System.in);

		long A = sc.nextLong();
		long B = sc.nextLong();
		long N = sc.nextLong();
		long [] left =new long[1000000000];
		long [] right =new long[1000000000];
		long leftMax = 0;
		long rightMin = 0;

		for(int i = 1; i <= N; i++) {
			left[i-1] = A * i / B;
			if(i > 1) {
				leftMax = Math.max(leftMax,left[i-1]);
			}else if(i == 1){
				leftMax = left[i-1];
			}

			right[i-1] = i / B;
			if(i > 1) {
				rightMin = Math.min(rightMin,right[i-1]);
			}else if(i == 1){
				rightMin = right[i-1];
			}
		}
		System.out.println(leftMax - rightMin);
		sc.close();
	}
}