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.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
 
namespace Main
{
    public static class Program
    {
        static void Main(string[] args)
        {

            int[] abn = GetIntList(Console.ReadLine());
            var a = abn[0];
            var b = abn[1];
            var n = abn[2];

            double answer = 0;
            double preanswer = 0;
            double x = 1;
            preanswer = Math.Floor(a*x/b) - Math.Floor(x/b);

            while(true){
                x++;
                answer = Math.Floor(a*x/b) - a*Math.Floor(x/b);
                if(answer <= preanswer){
                    break;
                }
                else{
                    preanswer = answer;
                }
                if(x>n){
                    break;
                }
                
            }
            Console.WriteLine((int)preanswer);
 
        }
        #region libraries
        private static int[] GetIntList(string line)
        {
            return line.Split(' ').Select(x => int.Parse(x)).ToArray();
 
        }
        private static double[] GetDoubleList(string line)
        {
            return line.Split(' ').Select(x => double.Parse(x)).ToArray();
 
        }
        private static ulong[] GetUlongList(string line)
        {
            return line.Split(' ').Select(x => ulong.Parse(x)).ToArray();
        }
        private static long[] GetLongList(string line)
        {
            return line.Split(' ').Select(x => long.Parse(x)).ToArray();
        }
        private static int SearchNearest(this IEnumerable<int> list, int target)
        {
            var min = list.Min(c => Math.Abs(c - target));
            return list.First(c => Math.Abs(c - target) == min);
        }
        public static bool IsOdd(int i)
        {
            return i % 2 == 1 ? true : false;
        }
        public static int Gcd(int a,int b)
        {
            if(a < b)
            {
                Gcd(b, a);
            }
            while (b != 0)
            {
                var rm = a % b;
                a = b;
                b = rm;
            }
            return a;
        }
        #endregion libraries
    }
}