class Solution {
    private enum Operation {
        Append,
        Delete
    }
    
    static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        
        var numberOfInputs = Int32.Parse(Console.ReadLine()!);
        var theString = string.Empty;
        var operations = new Stack<(Operation, string)>();
        
        for (var _ = 0; _ < numberOfInputs; _++)
        {
            var operation = Console.ReadLine()!.Split();
            
            switch (operation[0])
            {
                case "1":
                    theString += operation[1];
                    operations.Push(new (Operation.Append, operation[1]));
                    continue;
                case "2":
                    var k = Int32.Parse(operation[1]);
                    var stringToRemove = theString[(theString.Length - k)..];
                    theString = theString.Substring(0, theString.Length - k);
                    operations.Push(new (Operation.Delete, stringToRemove));
                    continue;
                case "3":
                    k = Int32.Parse(operation[1]);
                    Console.WriteLine(theString[k - 1]);
                    continue; 
                case "4":
                    var theOperation = operations.Pop();
                    if (theOperation.Item1 == Operation.Append)
                    {
                        theString = theString.Substring(0, theString.Length - theOperation.Item2.Length);
                        continue;
                    }
                    theString += theOperation.Item2;
                    continue;
            }
        }
    }
}