import java.io.*;
class Node
{
    Node parent,left, right;
    String key;
    Node(String data)
    {
        parent=null;
        left=null;
        right=null;
        key=data;
    }
    void setLeft(Node a)
    {
        left=a;
    }
    void setRight(Node a)
    {
        right=a;
    }
    void setParent(Node a)
    {
        parent=a;
    }
}
class BinarySearchTree
{
    Node root;
    BinarySearchTree()
    {
        root=null;
    }
    Node search(String a)
    {
        Node x=root;
        while(x!=null)
        {
            if(x.key.equals(a))
            {
                break;
            }
            if(a.compareToIgnoreCase(x.key)<0)
            {
                x=x.left;
            }
            else
            {
                x=x.right;
            }
        }
        return x;
    }
    Node Minimum(Node x)
    {

        while(x.left!=null)
        {
            x=x.left;
        }
        return x;
    }
    Node Maximum(Node x)
    {

        while(x.right!=null)
        {
            x=x.right;
        }
        return x;
    }

    Node successor(Node a)
    {
        Node x=null;
        Node y=null;
        if(a.right!=null)
        {
            x=a.right;
            return Minimum(x);
        }
        else
        {

            y=a.parent;
            x=a;
            while(y!=null)
            {
                x=y;
                y=y.parent;
                if(y.left==x)
                {
                    break;
                }
            }
        }
        return y;
    }
    // Node predecessor(Node a)
    // {
    //  Node x=null;
    //  Node y=null;
    //  if(a.left!=null)
    //  {
    //      x=a.left;
    //      return Maximum(a);
    //  }
    //  else
    //  {
    //      x=a;
    //      y=x.parent;
    //      while(y!=null&&y.left.key.equals(x.key))
    //      {
    //          x=y;
    //          y=y.parent;
    //      }
    //  }
    //  return y;
    // }
    void insert(Node a)
    {
        Node x=root;
        Node y=root;
        while(x!=null)
        {
            y=x;
            if(a.key.compareToIgnoreCase(x.key)<0)
            {
                x=x.left;
            }
            else
            {
                x=x.right;
            }
        }
        if(y==null)
        {
            root=a;
        }
        else if(a.key.compareToIgnoreCase(y.key)<0)
        {
            a.setParent(y);
            y.setLeft(a);
        }
        else
        {
            a.setParent(y);
            y.setRight(a);
        }

    }
    void Replace(Node a, Node b)
    {
        if(a.parent==null)
        {
            root=b;
        }
        else if(a.parent.left!=null)
        {
            if(a.parent.left.key.equals(a.key))
            {
                a.parent.left=b;
            }
        }
        else if(a.parent.right!=null)
        {
            if(a.parent.right.key.equals(a.key))
            {
                a.parent.right=b;
            }
        }
        if(a.parent!=null)
            b.parent=a.parent;
    }
    void delete(Node a)
    {
        Node x=null;
        x=a.parent;
        if(a.left==null&&a.right==null)
        {
            Replace(a,null);
        }
        else if(a.left!=null&&a.right==null)
        {
            Replace(a,a.left);
        }
        else if(a.left==null&&a.right!=null)
        {
            Replace(a,a.right);
        }
        else
        {
            Node y=successor(a);
            if(y.key.equals(a.right.key))
            {
                y.left=a.left;
                Replace(a,y);
            }
            else
            {
                delete(y);
                y.left=a.left;
                if(a.left!=null)
                    y.left.parent=y;
                y.right=a.right;
                if(a.right!=null)
                    y.right.parent=y;
                Replace(a,y);
            }
        }
    }
    void inorder(Node a)
    {
        if(a==null)
            return;
        inorder(a.left);
        System.out.println(a.key);
        inorder(a.right);

    }
    Node findSmallest(String a)
    {
        Node x=root;
        Node min=null;
        while(x!=null)
        {
            if(a.compareToIgnoreCase(x.key)<0)
            {
                min=x;
                x=x.left;
            }
            else
            {
                x=x.right;
            }
        }
        return min;
    }
}
class Ass3_1
{
    public static void main(String args[])throws IOException
    {
        InputStreamReader isr=new InputStreamReader(System.in);
        BufferedReader br=new BufferedReader(isr);
        BinarySearchTree T= new BinarySearchTree();
        int b=Integer.parseInt(br.readLine());
        String word="";
        int i,j;
        int len=0;
        Node x;
        String a="";
        char ch=' ';
        for(i=0;i<b;i++)
        {
            a=br.readLine();
            len=a.length();
            for(j=1;j<len;j++)
            {
                word+=a.charAt(j);
            }
            ch=a.charAt(0);
            if(ch=='+')
                T.insert(new Node(word));
            else if(ch=='-')
            {
                x=T.search(word);
                if(x!=null)
                    T.delete(x);
            }
            else if(ch=='>')
            {
                    x=T.findSmallest(word);
                    if(x!=null)
                        System.out.println(x.key);
                    else
                        System.out.println("ERROR");
            }
            else if(ch=='?')
            {
                x=T.search(word);
                if(x!=null)
                {
                    System.out.println(word);
                }
                else
                {
                    System.out.println("ERROR");
                }
            }
            else if(a.equals("."))
            {
                break;
            }
                word="";
        }
        T.inorder(T.root);
    }
}