class Solution {
    static void Main(String[] args) {
        
        var linkedList = new LinkedList<string>();
        var queries = int.Parse(Console.ReadLine());
        
        for (var i = 0; i < queries; i++) {
            var ops = Console.ReadLine().Split();
            
            switch(ops[0]) {
                case "1":
                    Append(linkedList, ops[1]);
                    break;
                case "2":
                    DeleteCharacters(linkedList, int.Parse(ops[1]));
                    break;
                case "3":
                    Print(linkedList, int.Parse(ops[1])-1);
                    break;
                case "4":
                    UndoOperation(linkedList);
                    break;   
            }
        }
        
        static void Append(LinkedList<string> l, string data) {
            var s = data;
            if (l.Last != null) {
                s = $"{l.Last.Value}{data}";
            }
            
            l.AddLast(s);
        }
        
        static void DeleteCharacters(LinkedList<string> l, int k) {
            if (l.Last == null) {
                return;
            }
            
            var s = l.Last.Value;
            var index = s.Length - k;
            s = s.Remove(index);
            l.AddLast(s);
        }
        
        static void Print(LinkedList<string> l, int index) {
            if (l.Last == null) {
                return;
            }
            
            var s = l.Last.Value[index];
            Console.WriteLine(s);
        }
        
        static void UndoOperation(LinkedList<string> l)
        {
            if (l.Last == null) {
                return;
            }
            
            l.RemoveLast();
        }
    }
}