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 C# (.NET Core 3.1.201) (judge verdict: Time Limit Exceeded)

using System;
using System.Linq;

public class Test
{
	public static void Main()
	{
		// my code goes here
		
		var x = Console.ReadLine().Split().Select(y => double.Parse(y)).ToArray();
		double a = x[0];
		double b = x[1];
		double n = x[2];
		double max = 0;
		double c = 0;
		
		for(int i=(int)n; i!=-1; i--){
			c = Math.Floor((a*i)/b) - (a*Math.Floor(i/b));
			if(c>max){max = c;}
		}
		
		Console.WriteLine(max);
		
	}
}