4
1 4
3 1
3 4
 5
4 1
4 3
5 3
2 4
 21
7 15
13 1
14 3
4 10
2 3
16 18
17 20
16 20
8 4
3 12
2 17
13 11
16 1
13 2
13 5
8 9
6 14
3 17
16 9
13 8
 3
3 1
3 2
 6
5 2
5 3
1 4
3 1
5 6
 60
17 34
46 22
50 44
46 33
41 21
31 33
48 6
38 19
35 60
2 24
49 29
7 53
34 1
19 55
32 1
31 42
27 28
4 53
6 50
21 34
1 10
12 36
54 8
16 13
51 43
45 51
54 20
13 53
34 33
49 33
51 11
59 34
15 5
59 28
30 39
13 30
58 4
34 14
3 9
19 34
4 18
26 48
56 54
3 43
57 25
3 41
35 3
48 44
19 13
54 1
23 31
59 47
5 1
46 40
6 26
20 25
37 5
17 24
20 52
 3
3 2
1 2
 39
6 13
15 39
10 35
31 28
4 21
12 39
3 7
3 13
6 1
5 14
36 28
12 15
18 38
30 29
19 34
36 16
20 22
8 13
38 32
26 39
21 37
1 7
15 27
12 26
8 3
6 14
29 2
25 23
32 21
5 16
32 25
6 8
13 10
23 30
34 37
29 33
28 14
36 5
 10
5 9
8 5
7 6
7 9
3 9
2 1
7 2
3 6
7 1

1
3 4 1 2  0
 3
13 2 1 7 3 17 1 19 13 8 1 21  0
 0
 2
48 44 1 6 6 26 1 12  0
 7
12 15 1 2 1 7 1 9 12 26 1 11 8 3 1 12 6 8 1 17 28 14 1 20 36 5 1 24  2
3 6 1 4 7 1 1 10 

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class RoadsNotOnlyBerland<V> {

    private static int n;

    private static Node<Integer>[] cities;

    private static List<Road> buildeds = new ArrayList<Road>();

    private static List<Road> closeds = new ArrayList<Road>();;

    private static RoadsNotOnlyBerland<Integer> berland = new RoadsNotOnlyBerland<Integer>();

    private static class Node<V> {

	V node;

	Node<V> parent;

	int rank;

	public Node() {
	    this.parent = this;
	}
    }

    public Node<V> makeSet(V x) {

	Node<V> node = new Node<V>();

	node.node = x;
	node.parent = node;
	node.rank = 0;

	return node;
    }

    public void link(Node<V> x, Node<V> y) {

	if (x.rank > y.rank) {
	    y.parent = x;
	} else {
	    x.parent = y;
	    if (x.rank == y.rank) {
		y.rank++;
	    }
	}
    }

    public Node<V> findSet(Node<V> x) {

	if (x.parent != x) {
	    x.parent = findSet(x.parent);
	}

	return x.parent;
    }

    public void union(Node<V> x, Node<V> y) {

	Node<V> rtX = findSet(x);
	Node<V> rtY = findSet(y);
	if (rtX.parent != rtY.parent) {
	    link(rtX, rtY);
	}
    }

    public V getNode(Node<V> x) {
	return x.node;
    }

    private static Node<Integer> get(int key) {

	Node<Integer> node = cities[key];

	if (node == null) {
	    node = berland.makeSet(key);
	    cities[key] = node;
	}

	return node;
    }

    private static boolean connected(Node<Integer> from, Node<Integer> to) {

	boolean valid;

	Node<Integer> key1 = berland.findSet(from);
	Node<Integer> key2 = berland.findSet(to);
	valid = (key1.node == key2.node);

	return valid;
    }

    private static class Road {

	Node<Integer> from;

	Node<Integer> to;

	public Road(Node<Integer> from, Node<Integer> to) {
	    this.from = from;
	    this.to = to;
	}

	public void union() {
	    berland.union(from, to);
	}
    }

    private static void print() {

	int size = closeds.size();
	Road closed;
	Road built;
	for (int i = 0; i < size; i++) {
	    closed = closeds.get(i);
	    built = buildeds.get(i);
	    System.out.format("%s %s %s %s", closed.from.node, closed.to.node,
		    built.from.node, built.to.node);
	}
    }

    private static void readRoads(Scanner scanner) {

	int l = n - 1;
	Road road;
	int key1;
	int key2;
	Node<Integer> from;
	Node<Integer> to;
	for (int i = 1; i <= l; i++) {
	    key1 = scanner.nextInt();
	    key2 = scanner.nextInt();
	    from = get(key1);
	    to = get(key2);
	    road = new Road(from, to);
	    if (connected(from, to)) {
		closeds.add(road);
	    } else {
		road.union();
	    }
	}
    }

    private static void buildRoads() {

	Node<Integer> first = get(1);
	Node<Integer> node;
	Road road;
	for (int i = 2; i <= n; i++) {
	    node = get(i);
	    if (!connected(first, node)) {
		road = new Road(first, node);
		road.union();
		buildeds.add(road);
	    }
	}
    }

    @SuppressWarnings("unchecked")
    public static void main(String[] args) {

	Scanner scanner = new Scanner(System.in);
	try {
	    n = scanner.nextInt();
	    int m = n + 1;
	    cities = (Node<Integer>[]) Array.newInstance(Node.class, m);
	    readRoads(scanner);
	    buildRoads();
	    print();
	} finally {
	    scanner.close();
	}
    }
}
