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: Accepted)

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 maxn = 0;
			long maxb = 0;
			
			maxn = Math.max(calc(a,b,n), calc(a,b,(n-1)));
			
			if(b<n) {
				maxb = Math.max(calc(a,b,b), calc(a,b,(b-1)));
			}
			
			System.out.println(Math.max(maxn, maxb));
			
			
		}
		
		static long calc(long a,long b, long n) {
			long res = 0;
			
			res = ((a*n)/b)-((n/b)*a);
			return res;
		}
		
	}