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: Runtime Error)

using System;
using System.Linq;

class A
{
    static void Main()
    {
        ulong[] P = Array.ConvertAll(Console.ReadLine().Split(' '), ulong.Parse);
        ulong A = P[0];
        ulong B = P[1];
        ulong N = P[2];
        int S = 0;
        decimal[] Temp = new decimal[N];
        for (double i = 1; i <= N; i++)
        {
            double Ax = A * i;
            decimal TempX;
            TempX = (decimal)Math.Floor(A * i / B) - (decimal)(A * Math.Floor(i / B));
            Temp[S] = TempX;
        }
        Console.WriteLine(Temp.Max());
    }
}