static void Main(string[] args)
{
var linesCount = int.Parse(Console.ReadLine());
for (int i = 0; i < linesCount; i++)
{
var line = Console.ReadLine();
var ocurDict = new Dictionary <char, int>();
// adding connections
for (int j = 0; j < line.Length; j++)
{
var ch = line[j];
ocurDict[ch] = ocurDict.ContainsKey(ch) ? ocurDict[ch] + 1 : 1;
if (!graph.ContainsKey(ch))
{
graph.Add(ch, new SortedSet <char>());
}
}
foreach (var kv in ocurDict)
{
occurs[kv.Key] = occurs.ContainsKey(kv.Key) ? Math.Max(occurs[kv.Key], ocurDict[kv.Key]) : ocurDict[kv.Key];
}
}
var bag = new OrderedSet <char>(startElements.Difference(endElements));
while (bag.Count > 0)
{
var nextQueue = new OrderedSet <char>();
foreach (var nextPoint in bag)
{
allAnswers.Add(nextPoint);
nextQueue.AddMany(graph[nextPoint]);
}
bag = nextQueue;
}
Console.WriteLine(string.Join("", allAnswers));
}