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;
using System.Linq;
public static class P
{
    public static void Main()
    {
        double[] a;
        a = Console.ReadLine().Split(' ').Select(s => double.Parse(s)).ToArray();
        double m=0;
        double t=0;
        for(int i = 1; i <= a[2] + 1; i++)
        {
            t = Math.Floor((double)a[0] * i / a[1])- a[0] * Math.Floor((double)(i / a[1]));
            if (m < t)m = t;
        }
        Console.WriteLine(m);
    }
}