Problem:
Score : 200 points

Problem Statement

A string is called a KEYENCE string when it can be changed to keyence by removing its contiguous substring (possibly empty) only once.

Given a string S consisting of lowercase English letters, determine if S is a KEYENCE string.

Constraints

The length of S is between 7 and 100 (inclusive).

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

S

Output

If S is a KEYENCE string, print YES; otherwise, print NO.

Sample Input 1

keyofscience

Sample Output 1

YES

keyence is an abbreviation of key of science.

Sample Input 2

mpyszsbznf

Sample Output 2

NO

Sample Input 3

ashlfyha

Sample Output 3

NO

Sample Input 4

keyence

Sample Output 4

YES

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace KEYPC2019_B
{
    class Program
    {
        static void Main(string[] args)
        {
            var S = Console.ReadLine();
            var keystr = "keyence";

            if (S.Contains(keystr))
            {
                var newS = S.Replace(keystr, "K");
                if (newS.IndexOf('K') == 0 || newS.IndexOf('K') == newS.Length - 1)
                {
                    Console.WriteLine("YES");
                }
                else
                {
                    Console.WriteLine("NO");
                }
                return;
            }

            for (int i = 0; i < S.Length; i++)
            {
                var t = 0;
                while (S[i + t] == keystr[t])
                {
                    t++;
                }

                if (t != 0)
                {
                    var sec = keystr.Substring(t, keystr.Length - t);

                    if (S.Contains(sec))
                    {
                        if (i != 0)
                        {
                            Console.WriteLine("NO");
                            return;
                        }
                        Console.WriteLine("YES");
                        return;
                    }
                }
            }

            Console.WriteLine("NO");
        }
    }
}