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;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            List<long> abn = Console.ReadLine().Split().Select(s => long.Parse(s)).ToList(); 
            long max = 0;
            /*
            for (int i = 1; i <= abn[2]; i++)
            {

                long temp = Convert.ToInt64((Math.Floor((double)((abn[0] * i)/abn[1])) 
                    - (abn[0] * (Math.Floor((double)i / abn[1])))));
                if (temp >= max) max = temp;
            }*/


            max = Convert.ToInt64((Math.Floor((double)((abn[0] * abn[2]) / abn[1]))));

            Console.WriteLine(max);

        }
    }
}