static void Main()
{
var n = int.Parse(Console.ReadLine());
var set = new IndexedSet <int>();
Console.SetOut(new System.IO.StreamWriter(Console.OpenStandardOutput())
{
AutoFlush = false
});
while (n-- > 0)
{
var q = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
if (q[0] == 0)
{
set.Add(q[1]);
Console.WriteLine(set.Count);
}
else if (q[0] == 1)
{
Console.WriteLine(set.Contains(q[1]) ? 1 : 0);
}
else if (q[0] == 2)
{
set.Remove(q[1]);
}
else
{
foreach (var x in set.GetItems(x => x >= q[1], x => x <= q[2]))
{
Console.WriteLine(x);
}
}
}
Console.Out.Flush();
}