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: Accepted)

using System;

namespace D
{
    class Program
    {
        static void Main(string[] args)
        {
            var ABN = Array.ConvertAll(Console.ReadLine().Split(' '), long.Parse);
            var A = ABN[0]; var B = ABN[1]; var N = ABN[2];
            if (B - 1 <= N) Console.WriteLine(calc(B - 1, A, B));
            else Console.WriteLine(calc(N, A, B));
        }

        static long calc(long x, long A, long B)
        {
            return ((A * x) / B) - A * (x / B);
        }
    }
}