C#でAtCoder Beginners Selection（ABC049C - 白昼夢）

####準備
[C#でAtCoderデビューのための準備]
(https://qiita.com/azumabashi/items/7aa9e4b77c10970cc30a)
のあとで AtCoder Beginners Selection　をやってみました。

####問題文
ABC049C - 白昼夢
[https://atcoder.jp/contests/abs/tasks/arc065_a]
(https://atcoder.jp/contests/abs/tasks/arc065_a)

####提出結果

using System;
 
class Program
{
    static void Main(string[] args)
    {
        string S = Console.ReadLine();
        // dream dreamer erase eraser
        string dm = "dream";
        string dmr = "dreamer";
        string er = "erase";
        string err = "eraser";
        int dml = dm.Length;
        int dmrl = dmr.Length;
        int erl = er.Length;
        int errl = err.Length;
        string chkS = S;
        string result = "YES";
        while (true)
        {
            if (chkS.Length >= dml)
            {
                if (chkS.Substring(chkS.Length - dml, dml) == dm)
                {
                    if (chkS.Length == dml)
                    {
                        break;
                    }
                    else
                    {
                        chkS = chkS.Substring(0, chkS.Length - dml);
                        continue;
                    }
                }
            }
            if (chkS.Length >= dmrl)
            {
                if (chkS.Substring(chkS.Length - dmrl, dmrl) == dmr)
                {
                    if (chkS.Length == dmrl)
                    {
                        break;
                    }
                    else
                    {
                        chkS = chkS.Substring(0, chkS.Length - dmrl);
                        continue;
                    }
                }
            }
            if (chkS.Length >= erl)
            {
                if (chkS.Substring(chkS.Length - erl, erl) == er)
                {
                    if (chkS.Length == erl)
                    {
                        break;
                    }
                    else
                    {
                        chkS = chkS.Substring(0, chkS.Length - erl);
                        continue;
                    }
                }
            }
            if (chkS.Length >= errl)
            {
                if (chkS.Substring(chkS.Length - errl, errl) == err)
                {
                    if (chkS.Length == errl)
                    {
                        break;
                    }
                    else
                    {
                        chkS = chkS.Substring(0, chkS.Length - errl);
                        continue;
                    }
                }
            }
            result = "NO";
            break;
        }
                 
        Console.WriteLine($"{result}");
    }
}

####テスト実行