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;

class Program {
    public static void Main() {
        const string keyence = "keyence";
        string s = Console.ReadLine();

        bool hit = false;
        int life = 1;
        int looked = 0;
        for (int i = 0; i < keyence.Length; i++) {
            for (int j = looked; j < s.Length; j++) {
                if (keyence[i] == s[j]) {
                    hit = true;
                    looked = j+1;
                    if (i == keyence.Length-1) {
                        Console.WriteLine("YES");
                        return;
                    }
                    break;
                }

                if (hit) {
                    hit = false;
                    life--;
                    if (life < 0) {
                        break;
                    }
                }
            }
            
            if (life < 0) {
                break;
            }
        }
        
        // 後ろから見る
        hit = false;
        life = 1;
        looked = s.Length-1;
        for (int i = keyence.Length-1; i >= 0; i--) {
            for (int j = looked; j >= 0; j--) {
                if (keyence[i] == s[j]) {
                    hit = true;
                    looked = j-1;
                    if (i == 0) {
                        Console.WriteLine("YES");
                        return;
                    }
                    break;
                }

                if (hit) {
                    hit = false;
                    life--;
                    if (life < 0) {
                        Console.WriteLine("NO");
                        return;
                    }
                }
            }
        }
        
        Console.WriteLine("NO");
    }
}