/**
 * Created by leon on 1/23/18.
 */
import java.util. *;
public class PhoneBook {
    
    TreeMap<String, String> phoneBook = new TreeMap<String, String>();
    
    public String add(String name, String number) {
        phoneBook.put(name, number);
        return name + " " + number;
    }
    
    public String remove(String name) {
        phoneBook.remove(name);
        return name;
        
    }
    
    public String lookup(String name) {
        return phoneBook.get(name);
        
        
    }
    
    public String reverseLookup(String number) {
        for(Map.Entry<String, String> entry : phoneBook.entrySet()) {
            String value = entry.getValue();
            if(value.equals(number)) {
                return entry.getKey();
            }
        }
        return "";
    }
    
    public void display() {
        for(Map.Entry<String, String> entry : phoneBook.entrySet()) {
            String value = entry.getValue();
            System.out.println(entry.getKey() + " -> " + entry.getValue());
        }
    }
    
    
}