using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var wordDictionary = new HashSet<string> {"a", "aa", "aaa"};

        var wordDictionary2 = new HashSet<string> {"hot", "tap", "pan"};

        Console.WriteLine(validWord(wordDictionary, "abc"));

        Console.WriteLine(validWord(wordDictionary2, "aaaaakjdfhakhotnkjdas"));

    }

    public static int validWord(HashSet<string> dictionary, string query)

    {

        string longestSubstr = "";

        string substr = "";

​

        for (int i = query.Length; i > 0; i--)

        {

            for (int start = 0; start <= query.Length - i; start++)

            {

                substr = query.Substring(start, i);

                if (dictionary.Contains(substr) && longestSubstr.Length < substr.Length)

                {

                    longestSubstr = substr;

                    i = 0;

                    break;

                }

            }

        }

​

        return longestSubstr.Length == 0 ? 0 : query.Length - longestSubstr.Length;

    }

​

}