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# (Mono-csc 3.5.0) (judge verdict: Accepted)

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

class Program
{
    public static void Main()
    {
        var a = Read.Long();
        var b = Read.Long();
        var n = Read.Long();
        long x = Min(b - 1, n);
        long result = (long)((a * x) / (double)b) - a * (long)(x / (double)b);
        WriteLine($"{result}");
    }
}

static class Read
{
    static Queue<string> queue = new Queue<string>();
    static void Enqueue()
    {
        ReadLine().Split(' ').ToList().ForEach(a => queue.Enqueue(a));
    }
    public static int Int()
    {
        if(queue.Count == 0)
            Enqueue();
        return int.Parse(queue.Dequeue());
    }
    public static long Long()
    {
        if(queue.Count == 0)
            Enqueue();
        return long.Parse(queue.Dequeue());
    }
    public static double Double()
    {
        if(queue.Count == 0)
            Enqueue();
        return double.Parse(queue.Dequeue());
    }
    public static string String()
    {
        if(queue.Count == 0)
            Enqueue();
        return queue.Dequeue();
    }
}