import java.util.*;
import java.lang.*;
 
class Main
{
	public static void main (String[] args) throws java.lang.Exception
	{
    List<Integer> list1 = Arrays.asList(1, 2, 3, 4);
    List<Integer> list2 = Arrays.asList(2, 3, 4, 6, 7);
    List<Integer> union = new ArrayList<Integer>(list1);
    union.addAll(list2);
    List<Integer> intersection = new ArrayList<Integer>(list1);
    intersection.retainAll(list2);
    union.removeAll(intersection);
    for (Integer n : union) {
        System.out.println(n);
    }
	}
}

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