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: Accepted)

using System;

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

            var iskey = false;
            if (S.Contains(keystr))
            {
                var newS = S.Replace(keystr, "K");
                if (newS.IndexOf('K') == 0 || newS.IndexOf('K') == newS.Length - 1)
                {
                    iskey = true;
                }
            }

            for (int i = 1; i < keystr.Length; i++)
            {
                var targetleft = keystr.Substring(0, i);
                var targetright = keystr.Substring(i, keystr.Length - i);

                if (!(S.Contains(targetleft) && S.Contains(targetright)))
                {
                    continue;
                }

                if (S.IndexOf(targetleft) != 0)
                {
                    continue;
                }

                var newS = S.Replace(targetright, "R");
                if (newS.LastIndexOf('R') != newS.Length - 1)
                {
                    continue;
                }

                iskey = true;
            }

            Console.WriteLine(iskey ? "YES" : "NO");
        }
    }
}