import java.util.*;

public class Dict<K,V> {
  private List<Entry<K,V>> elements;
  
  public Dict() {
    elements = new ArrayList<Entry<K,V>>();
  }
  
  public void add(K key, V value){
    if (lookup(key) == null)
      elements.add(new Entry(key, value));
  }
  
  public V lookup(K key) {
    for (Entry<K,V> e : elements)
      if (key.equals(e.getKey()))
      return e.getValue();
    return null;
  }
  
}