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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            long A, B, N;
            long result, max=0;
            string[] str = Console.ReadLine().Split(' ');
            A = long.Parse(str[0]);
            B = long.Parse(str[1]);
            N = long.Parse(str[2]);

            for(long x = 1; x < 100000000000; x++)
            {
                result = floor(A, B, x) - A * floor(1, B, x);
                if (max < result) max = result;
            }
            Console.WriteLine(max);
        }
        static long floor(long A,long B,long x)
        {
            long result=0;
            result = (long)(A * x / B);
            return result;
        }
    }
}