using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;

class Program
{
	static void Main(string[] args)
	{
		new Program().Solve();
	}

	void Solve()
	{
		string s = Console.ReadLine();
		char c = 'ｗ';
		int i = 0;
		int n = s.Length;
		List<string> ans = new List<string>();
		int len = 0;
		while (i < n)
		{
			if (s[i] == c)
			{
				i++;
				continue;
			}
			int j = i;
			while (i < n && s[i] != c) i++;
			int k = i;
			while (i < n && s[i] == c) i++;
			if (i - k == 0) continue;
			if (len == (i - k))
			{
				len = i - k;
				ans.Add(s.Substring(j, k - j));
			}
			else if (len < (i - k))
			{
				len = i - k;
				ans.Clear();
				ans.Add(s.Substring(j, k - j));
			}
		}
		if (ans.Count == 0)
		{
			Console.WriteLine();
		}
		else
		{
			foreach (string item in ans)
			{
				Console.WriteLine(item);
			}
		}
	}
}