Problem:
Score : 100 points

Problem Statement

Given a lowercase English letter c, determine whether it is a vowel. Here, there are five vowels in the English alphabet: a, e, i, o and u.

Constraints

c is a lowercase English letter.

Input

The input is given from Standard Input in the following format:

c

Output

If c is a vowel, print vowel. Otherwise, print consonant.

Sample Input 1

a

Sample Output 1

vowel

Since a is a vowel, print vowel.

Sample Input 2

z

Sample Output 2

consonant

Sample Input 3

s

Sample Output 3

consonant

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

using System;

class Daydream {
    static void Main() {
        string input = Console.ReadLine();

        string reverse_string = "";

        // input を逆順にして格納
        for(int i = 0; i < input.Length; i++) {
            reverse_string = input[i] + reverse_string;
        }
        
        // 比較する文字列をひっくり返して長い順に配列に格納
        string[] comparison_string = { "remaerd", "resare", "maerd", "esare" };

        
        for(int i = 0; i < reverse_string.Length; i++) {
            if (reverse_string.IndexOf("remaerd") == 0) {
                reverse_string = ReplaceOnce(reverse_string, "remaerd", "");
                i = 0;
            }

            if (reverse_string.IndexOf("resare") == 0) { 
                reverse_string = ReplaceOnce(reverse_string,"resare", "");
                i = 0;
            }

            if (reverse_string.IndexOf("maerd") == 0) {
                reverse_string = ReplaceOnce(reverse_string, "maerd", "");
                i = 0;
            }

            if (reverse_string.IndexOf("esare") == 0) {
                reverse_string = ReplaceOnce(reverse_string, "esare", "");
                i = 0;
            }
        }
        

        if(reverse_string == "") {
            Console.WriteLine("YES");
        } else {
            Console.WriteLine("NO");
        }
                
    }

    static string ReplaceOnce(string input, string old_string, string new_string) {
        int start_index = input.IndexOf(old_string);
        int end_index   = start_index + old_string.Length;

        string result = "";
        result += input.Substring(0, start_index);
        result += new_string;
        result += input.Substring(end_index);

        return result;
    }
}