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: Accepted)

using System;
using System.Text;
using System.Collections.Generic;
using System.Collections;
using static System.Math;
using System.Linq;
using static System.Array;

namespace ConsoleApp2
{
    class Program
    {
    

        static void Main(string[] args)
        {
            //N = long.Parse(Console.ReadLine());
            //var c = Console.ReadLine();
            var ABN = Console.ReadLine().Split(' ').Select(x => double.Parse(x)).ToArray();
            var A = ABN[0];
            var B = ABN[1];
            var N = ABN[2];

            //for (int i = 1; i <= N; i++)
            //{
            //    Console.WriteLine(Floor((A*i/B))-A*Floor(i/B));
            //}
            Console.WriteLine(Floor((A * Min(N,B-1) / B)));
        }



    }

}