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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ABC165
{
    class Program
    {
        static void Main(string[] args)
        {
            d();
        }

        public static void d()
        {
            double[] abn = Console.ReadLine().Split(' ').Select(double.Parse).ToArray();
            double a = abn[0], b = abn[1], n = abn[2];
            double max = 0;
            int j = 0;
            for(double i = n; j < 1000 ; i =Math.Floor(i/ 2))
            {
                double x = Math.Floor(a * i / b) - a * Math.Floor(i / b);
                max = Math.Max(max, x);
                j++;
            }
            Console.WriteLine(max);
        }
    }
}