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;
using System.Collections.Generic;


class Program
{
    static void Main(string[] args)
    {
        string[] ABN = Console.ReadLine().Split(' ');
        ulong A = ulong.Parse(ABN[0]);
        ulong B = ulong.Parse(ABN[1]);
        ulong N = ulong.Parse(ABN[2]);

        double anB = (double)A * (double)N/B;
        ulong f = (ulong)anB;

        ulong l = N / B;
        l *= A;

        Console.WriteLine( f - l );


        /*
        int maxValue = 0;
        int value;

        for(ulong x=0; x<=N; x++){
            ulong f = A * x / B;

            ulong l = x / B;
            l *= A;

            Console.WriteLine(f-l);
            Console.WriteLine(x);
        }
        */
    }
}