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.util.*;

public class ConnectedComponents

{

    static final int MAXV         = 100;

    static boolean   processed[]  = new boolean[MAXV];

    static boolean   discovered[] = new boolean[MAXV];

    static int       parent[]     = new int[MAXV];



    static void bfs(CCGraph g, int start)

    {

        Queue<Integer> q = new LinkedList<Integer>();

        int i, v;

        q.offer(start);

        discovered[start] = true;

        while (!q.isEmpty())

        {

            v = q.remove();

            process_vertex(v);

            processed[v] = true;

            for (i = g.degree[v] - 1; i >= 0; i--)

            {

                if (!discovered[g.edges[v][i]])

                {

                    q.offer(g.edges[v][i]);

                    discovered[g.edges[v][i]] = true;

                    parent[g.edges[v][i]] = v;

                }

            }

        }

    }



    static void initialize_search(CCGraph g)

    {

        for (int i = 1; i <= g.nvertices; i++)

        {

            processed[i] = discovered[i] = false;

            parent[i] = -1;

        }

    }



    static void process_vertex(int v)

    {

//        System.out.printf(" %d", v);

    }



    static void connected_components(CCGraph g)

    {

        int c;

        initialize_search(g);

        c = 0;

        ArrayList<Integer> ans = new ArrayList<>();
        for (int i = 1; i <= g.nvertices; i++) {
            if (!discovered[i]) {
                c++;
                bfs(g,i);
                ans.add(i);
            }
        }

        System.out.println(c - 1);
//        System.out.println(ans);
        for (int i = 0; i < c - 1; i++) {
//            System.out.printf("Component %d:", c);

//            bfs(g, );
            System.out.println(ans.get(i) + " " + g.edges[ans.get(i)][0] + " " + ans.get(i) + " " + ans.get(i + 1));
        }

    }



    static public void main(String[] args)

    {

        CCGraph g = new CCGraph();

        g.read_CCGraph(false);

        g.print_CCGraph();

        connected_components(g);

    }

}
class CCGraph

{

    static final int MAXV      = 100;

    static final int MAXDEGREE = 50;

    public int       edges[][] = new int[MAXV + 1][MAXDEGREE];

    public int       degree[]  = new int[MAXV + 1];

    public int       nvertices;

    public int       nedges;



    CCGraph()

    {

        nvertices = nedges = 0;

        for (int i = 1; i <= MAXV; i++)

            degree[i] = 0;

    }



    void read_CCGraph(boolean directed)

    {

        int x, y;

        Scanner sc = new Scanner(System.in);

//        System.out.println("Enter the number of vertices: ");

        nvertices = sc.nextInt();

//        System.out.println("Enter the number of edges: ");
//
        int m = nvertices - 1;

//        System.out.println("Enter the edges: <from> <to>");

        for (int i = 1; i <= m; i++)

        {

            x = sc.nextInt();

            y = sc.nextInt();

            insert_edge(x, y, directed);

        }

        sc.close();

    }



    void insert_edge(int x, int y, boolean directed)

    {

//        if (degree[x] > MAXDEGREE)

//            System.out.printf(
//
//                    "Warning: insertion (%d, %d) exceeds max degree\n", x, y);

        edges[x][degree[x]] = y;

        degree[x]++;

        if (!directed)

            insert_edge(y, x, true);

        else

            nedges++;

    }



    void print_CCGraph()

    {

//        for (int i = 1; i <= nvertices; i++)
//
//        {
//
//            System.out.printf("%d: ", i);
//
//            for (int j = degree[i] - 1; j >= 0; j--)
//
//                System.out.printf(" %d", edges[i][j]);
//
//            System.out.printf("\n");
//
//        }

    }

}

