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# (Mono-mcs 6.8.0.105) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
using System.IO;
using static System.Console;

namespace atcorder2
{
    class Program
    {
        public static long Read()
        {
            return long.Parse(Console.ReadLine());
        }

        public static long[] Reads()
        {
            return Console.ReadLine().Split().Select(long.Parse).ToArray();
        }


        public static long gcd(long x, long y)
        {
            if (y < x) gcd(y, x);
            while (y != 0)
            {
                var z = x % y;
                x = y;
                y = z;
            }
            return x;
        }
        public static long keta(long x)
        {
            var z = 1;
            while (x > 0)
            {
                x /= 10;
                z++;
            }
            return z;
        }
        static void Main(string[] args)
        {
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);
            var abn = Reads();
            var a = abn[0];
            var b = abn[1];
            var n = abn[2];
            long x = 0;
            if (n >= b) x = b - 1;
            else x = n;
           
            WriteLine(Math.Floor((decimal)a * x / b) - a*Math.Floor((decimal)x / b));
            

            Console.Out.Flush();
        }
    }
}