using System; using System.IO; using System.Linq; using System.Collections.Generic; public class Program { public void Proc() { IsWin.Add(1, true); IsWin.Add(2, true); IsWin.Add(3, false); IsWin.Add(4, true); int num = int.Parse(Reader.ReadLine()); if(IsWin.ContainsKey(num)) { Console.WriteLine(IsWin[num]?"O":"X"); } else { Console.WriteLine((num % 4 == 3) ? "X":"O"); } } Dictionary dic = new Dictionary(); private bool GetAns(List num) { if(num.Count == 1) { return true; } if(num.Count == 0) { return false; } string key = string.Join("", num.Where(a=>a>0).OrderBy(a => a)); if(dic.ContainsKey(key)) { return dic[key]; } for (int i = 0; i < num.Count; i++) { for (int j = 1; j <= num[i]; j++) { List tmp = new List(); tmp.AddRange(num); tmp[i] -= j; if(!GetAns(tmp)) { dic[key] = true; return true; } } } dic[key] = false; return false; } Dictionary IsWin = new Dictionary(); public class Reader { private static StringReader sr; public static bool IsDebug = false; public static string ReadLine() { if (IsDebug) { if (sr == null) { sr = new StringReader(InputText.Trim()); } return sr.ReadLine(); } else { return Console.ReadLine(); } } private static string InputText = @" 3 "; } public static void Main(string[] args) { #if DEBUG Reader.IsDebug = true; #endif Program prg = new Program(); prg.Proc(); } }