import java.util.*;

public class ImmutableSet<E> implements Set<E> {

  public ImmutableSet(Collection<? extends E> c) {
    // your code here                                                                           
  }

  public ImmutableSet(E[] a) {
    // your code here                                                                           
  }

  public String toString() {
    // your code here
  }

  // ... all methods necessary for a Set                                                        

  // ... data field(s)                                                                          

}