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;

namespace D
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] line = Console.ReadLine().Split(' ');
            double a = double.Parse(line[0]);
            double b = double.Parse(line[1]);
            double n = double.Parse(line[2]);

            // double e = Math.Ceiling(a * n / b);
            // e = b < e ? b : e;

            double maxValue = double.MinValue;
            for(long i=0; i<=b; i++){
                double v = Math.Floor(a*(n-i)/b) - a * Math.Floor((n-i)/b);
                maxValue = maxValue<v ? v : maxValue;
            }
            Console.WriteLine(maxValue);
        }
    }
}