static void Main(String[] args) {
        /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution */
        
        int q = int.Parse(Console.ReadLine().Trim());
        
        Editor editor = new Editor();
        
        for(int i = 0; i < q; i++){
            string[] op = Console.ReadLine().Trim().Split(' ');
            
            editor.Execute(int.Parse(op[0]), op.Length > 1 ? op[1] : null);
        }
    }
    
    public class Editor {
        public string Text = string.Empty;
        public Stack<string> Undos = new Stack<string>();
        
        private ITextOperation[] operations = {
            new AppendOperation(),
            new DeleteOperation(),
            new PrintOperation(),
            new UndoOperation()
        };
        
        public void Execute(int opId, string p){
            operations[opId - 1].Execute(this, p);
        }
        
    }
    
    public interface ITextOperation{
        public void Execute(Editor editor, string val);
    }
    
    public class AppendOperation : ITextOperation {
        public void Execute(Editor editor, string val){
            editor.Undos.Push(editor.Text);
            editor.Text += val;
        }
    }
    public class DeleteOperation : ITextOperation {
        public void Execute(Editor editor, string val){
            int k = int.Parse(val);
            editor.Undos.Push(editor.Text);
            editor.Text = editor.Text.Remove(editor.Text.Length - k);
        }
    }
    public class PrintOperation : ITextOperation {
        public void Execute(Editor editor, string val){
            int k = int.Parse(val);
            Console.WriteLine(editor.Text[k-1]);
        }
    }
    public class UndoOperation : ITextOperation {
        public void Execute(Editor editor, string val){
            editor.Text = editor.Undos.Pop();
        }
    }