using System; using System.Collections.Generic; using System.Linq; namespace No371_1{ public class Program{ public static void Main(string[] args){ var sr = new StreamReader(); //--------------------------------- var l = sr.Next(); var h = sr.Next(); var pl = new List(); var tl = Enumerable.Range(2, (int)Math.Sqrt(h)).ToList(); var sqrt = (int)Math.Sqrt(Math.Sqrt(h)); while(tl[0] <= sqrt){ var p = tl[0]; pl.Add(p); tl.RemoveAll(x => x % p == 0); } pl.AddRange(tl); foreach(var p in pl.OrderByDescending(x => x)){ for(var i = h + h % 2 - 1; i >= l; i -= 2){ if(i != p && i % p == 0 && pl.TakeWhile(x => x < p).All(x => i / p % x != 0)) { Console.WriteLine(i); return; } } } Console.WriteLine(h - h % 2); //--------------------------------- } } public class StreamReader{ private readonly char[] _c = {' '}; private int _index = -1; private string[] _input = new string[0]; public T Next(){ if(_index == _input.Length - 1){ _index = -1; while(true){ string rl = Console.ReadLine(); if(rl == null){ if(typeof(T).IsClass) return default(T); return (T)typeof(T).GetField("MinValue").GetValue(null); } if(rl != ""){ _input = rl.Split(_c, StringSplitOptions.RemoveEmptyEntries); break; } } } return (T)Convert.ChangeType(_input[++_index], typeof(T), System.Globalization.CultureInfo.InvariantCulture); } } }