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.*;
import java.io.*;

public class RnB {
	
	public static void main( String[] args ) throws IOException {
		BufferedReader br = new BufferedReader( new InputStreamReader( System.in ) );
		PrintWriter pw = new PrintWriter( new BufferedWriter( new OutputStreamWriter( System.out ) ) );
		
		int N = Integer.parseInt(br.readLine() );
		
		ArrayList<Integer>[] map = new ArrayList[N];
		for(int i = 0; N > i; i++) {
			map[i] = new ArrayList<Integer>();
		}
		
		for(int i = 0; N-1 > i; i++) {
			String[] line = br.readLine().split(" ");
			int a = Integer.parseInt(line[0]) - 1;
			int b = Integer.parseInt(line[1]) - 1;
			
			map[a].add( b );
			map[b].add( a );
		}
		
		boolean[] isVisited = new boolean[N];
		Arrays.fill( isVisited, false );
		ArrayList<E> cyc = new ArrayList<E>();
		ArrayList<Integer> nc = new ArrayList<Integer>();
		for(int i = 0; N > i; i++) { 
			if( !isVisited[i] ) { //System.out.println("STARTING AT: " + i );
				if( i > 0 ) { //System.out.println("ADDING LONER..." );
					nc.add( i );
				}
				
				LinkedList<S> stack = new LinkedList<S>();
				stack.push( new S( i, -1 ) );
				while( stack.size() > 0 ) {
					S s = stack.pop(); //System.out.println("\tVISITING " + s.index + " from " + s.prev );
					if( isVisited[s.index] ) {
						continue;
					}
					
					isVisited[s.index] = true;
					
					ArrayList<Integer> m = map[s.index];
					for(int j = 0; m.size() > j; j++) {
						if( isVisited[m.get(j)] ) {
							if( m.get(j) != s.prev ) {
								cyc.add( new E(s.index, m.get(j)) ); //System.out.println("\t\tADDED: " + s.index + ", " + m.get(j) );
							}
						} else {
							stack.push( new S( m.get(j), s.index ) );
						}
					}
				}
			}
		}
		//System.out.println(cyc);
		pw.println( cyc.size() );
		for(int i = 0; cyc.size() > i; i++) {
			pw.print( cyc.get(i) );
			pw.print(" ");
			pw.print( cyc.get(i).a+1 );
			pw.print( " " );
			pw.println(nc.get(i)+1);
		}
		
		pw.close();
	}
}

class E {
	int a, b;
	public E( int a, int b ) {
		this.a = a;
		this.b = b;
	}
	
	public String toString() {
		return (a+1) + " " + (b+1);
	}
}

class S {
	int index, prev;
	public S( int index, int prev ) {
		this.index = index;
		this.prev = prev;
	}
}