import java.util.*;
public class Institution<T extends Person> implements Iterable<T>{

    Set<T> associates = new HashSet<T>();
    
    public Iterator<T> iterator(){
        return associates.iterator();
    }
    public void enroll(T c){
        associates.add( c );
    }
    
    public void withdraw(T c){
        associates.remove(c);
    }
    
    public <P extends T> void  merge(Institution<P> other){
        for(P person: other) {other.withdraw( person); this.enroll( person );}
    }
    
    public void test(){
        Institution<Person> ip = new Institution<Person>();
        Institution<Child> ic = new Institution<Child>();
        ip.merge(ic);
    }
}