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

namespace AtCoder.Abc
{
    class QuestionD
    {
        public static void Main(string[] args)
        {
            var sw = new System.IO.StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);

            // 文字列の入力
            //string s = Console.ReadLine();

            // 整数の入力
            //long n = long.Parse(Console.ReadLine());

            // 文字列配列の入力
            //string[] inputStrArray = Console.ReadLine().Split(' ');

            // 整数配列の入力
            var inputLongArray = Console.ReadLine().Split(' ').Select(i => long.Parse(i)).ToArray();

            long A = inputLongArray[0];
            long B = inputLongArray[1];
            long N = inputLongArray[2];

            long k;
            long max = 0;


            if (B > N)
            {
                max = (A * N) / B - A * (N / B);
            }

            else
            {
                for (k = 0; k * B - 1 < N; k++)
                {
                    max = (A * (k * B - 1)) / B - A * ((k * B - 1) / B);
                }
            }



            Console.WriteLine(max);

            Console.Out.Flush();
        }
    }
}