Problem:
Score : 100 points

Problem Statement

Takahashi is distributing N balls to K persons.

If each person has to receive at least one ball, what is the maximum possible difference in the number of balls received between the person with the most balls and the person with the fewest balls?

Constraints

1 \leq K \leq N \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K

Output

Print the maximum possible difference in the number of balls received.

Sample Input 1

3 2

Sample Output 1

1

The only way to distribute three balls to two persons so that each of them receives at least one ball is to give one ball to one person and give two balls to the other person.

Thus, the maximum possible difference in the number of balls received is 1.

Sample Input 2

3 1

Sample Output 2

0

We have no choice but to give three balls to the only person, in which case the difference in the number of balls received is 0.

Sample Input 3

8 5

Sample Output 3

3

For example, if we give 1, 4, 1, 1, 1 balls to the five persons, the number of balls received between the person with the most balls and the person with the fewest balls would be 3, which is the maximum result.

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

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

namespace codeTester
{
    class Program
    {
        static List<int> values = new List<int>();

        static void Main(string[] args)
        {
            values = IOUtilities.ReadSpaceSeparatedValues();
            Console.WriteLine(logic().ToString());
        }

        static int logic()
        {
            int ans = 0;
            if(values[1] == 1)
            {
                return 0;
            }
            return values[0] - values[1];
        }
    }

    class IOUtilities
    {
        public static List<int> ReadSpaceSeparatedValues()
        {
            List<int> values = new List<int>();
            string[] inputs = Console.ReadLine().Split(' ');
            foreach (string input in inputs)
            {
                values.Add(int.Parse(input));
            }

            return values;
        }

        public static List<int> ReadIndentationSeparatedValues(int num)
        {
            List<int> values = new List<int>();
            for (int i = 0; i < num; i++)
            {
                string input = Console.ReadLine();
                values.Add(int.Parse(input));
            }

            return values;
        }
    }

    class ListUtilities
    {
        /// <summary>
        /// list を index の位置で２つに分割します。
        /// </summary>
        /// <param name="list">分割されるリスト</param>
        /// <param name="index">分割位置（ 0 のとき１つめのリストは空になります）</param>
        /// <returns></returns>
        public static List<int>[] SeparateAt(List<int> list, int index)
        {
            return new[] { list.GetRange(0, index), list.GetRange(index, list.Count) };
        }
    }
}