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 ConsoleApp2
{
    class Program
    {
        static List<string> A = new List<string>();
        static int N = 0;
        static int M = 0;

        static void Main(string[] args)
        {
            string[] ABN = Console.ReadLine().Split(' ');
            double A = double.Parse(ABN[0]);
            double B = double.Parse(ABN[1]);
            double N = double.Parse(ABN[2]);

            double max = 0;

            for(double i = 0; i <= N; i++)
            {
                double answer = Math.Floor(A * i / B) - A * Math.Floor(i / B);

                if (answer > max)
                {
                    max = answer;
                }
            }

            Console.WriteLine(max);
        }
    }
}