Problem: Berland Government decided to improve relations with neighboring countries. First of all, it was decided to build new roads so that from each city of Berland and neighboring countries it became possible to reach all the others. There are n cities in Berland and neighboring countries in total and exactly n - 1 two-way roads. Because of the recent financial crisis, the Berland Government is strongly pressed for money, so to build a new road it has to close some of the existing ones. Every day it is possible to close one existing road and immediately build a new one. Your task is to determine how many days would be needed to rebuild roads so that from each city it became possible to reach all the others, and to draw a plan of closure of old roads and building of new ones.

Input

The first line contains integer n (2 ≤ n ≤ 1000) — amount of cities in Berland and neighboring countries. Next n - 1 lines contain the description of roads. Each road is described by two space-separated integers ai, bi (1 ≤ ai, bi ≤ n, ai ≠ bi) — pair of cities, which the road connects. It can't be more than one road between a pair of cities. No road connects the city with itself.

Output

Output the answer, number t — what is the least amount of days needed to rebuild roads so that from each city it became possible to reach all the others. Then output t lines — the plan of closure of old roads and building of new ones. Each line should describe one day in the format i j u v — it means that road between cities i and j became closed and a new road between cities u and v is built. Cities are numbered from 1. If the answer is not unique, output any.

Examples

Input

2
1 2


Output

0


Input

7
1 2
2 3
3 1
4 5
5 6
6 7


Output

1
3 1 3 7

Solution (in JAVA):

Solution:
/*
 * Hello! You are trying to hack my solution, are you? =)
 * Don't be afraid of the size, it's just a dump of useful methods like gcd, or n-th Fib number.
 * And I'm just to lazy to create a new .java for every task.
 * And if you were successful to hack my solution, please, send me this test as a message or to Abrackadabraa@gmail.com.
 * It can help me improve my skills and i'd be very grateful for that.
 * Sorry for time you spent reading this message. =)
 * Good luck, unknown rival. =)
 * */

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StreamTokenizer;
import java.io.Writer;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
import java.util.Set;
import java.util.SortedSet;
import java.util.Stack;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.Vector;

public class Abra {
	public static void main(String[] args) throws IOException {
		new Abra().run();
	}

	static class myLib {
		long fact(long x) {
			long a = 1;
			for (long i = 2; i <= x; i++) {
				a *= i;
			}
			return a;
		}

		long digitSum(String x) {
			long a = 0;
			for (int i = 0; i < x.length(); i++) {
				a += x.charAt(i) - '0';
			}
			return a;
		}

		long digitSum(long x) {
			long a = 0;
			while (x > 0) {
				a += x % 10;
				x /= 10;
			}
			return a;
		}

		long digitMul(long x) {
			long a = 1;
			while (x > 0) {
				a *= x % 10;
				x /= 10;
			}
			return a;
		}

		int digitCubesSum(int x) {
			int a = 0;
			while (x > 0) {
				a += (x % 10) * (x % 10) * (x % 10);
				x /= 10;
			}
			return a;
		}

		double pif(double ax, double ay, double bx, double by) {
			return Math.sqrt((ax - bx) * (ax - bx) + (ay - by) * (ay - by));
		}

		double pif3D(double ax, double ay, double az, double bx, double by, double bz) {
			return Math.sqrt((ax - bx) * (ax - bx) + (ay - by) * (ay - by) + (az - bz) * (az - bz));
		}

		double pif3D(double[] a, double[] b) {
			return Math.sqrt((a[0] - b[0]) * (a[0] - b[0]) + (a[1] - b[1]) * (a[1] - b[1]) + (a[2] - b[2]) * (a[2] - b[2]));
		}

		long gcd(long a, long b) {
			if (a == 0 || b == 0) return 1;
			if (a < b) {
				long c = b;
				b = a;
				a = c;
			}
			while (a % b != 0) {
				a = a % b;
				if (a < b) {
					long c = b;
					b = a;
					a = c;
				}
			}
			return b;
		}

		int gcd(int a, int b) {
			if (a == 0 || b == 0) return 1;
			if (a < b) {
				int c = b;
				b = a;
				a = c;
			}
			while (a % b != 0) {
				a = a % b;
				if (a < b) {
					int c = b;
					b = a;
					a = c;
				}
			}
			return b;
		}

		long lcm(long a, long b) throws IOException {
			return a * b / gcd(a, b);
		}

		int lcm(int a, int b) throws IOException {
			return a * b / gcd(a, b);
		}

		int countOccurences(String x, String y) {
			int a = 0, i = 0;
			while (true) {
				i = y.indexOf(x);
				if (i == -1) break;
				a++;
				y = y.substring(i + 1);
			}
			return a;
		}

		int[] findPrimes(int x) {
			boolean[] forErato = new boolean[x - 1];
			List<Integer> t = new Vector<Integer>();
			int l = 0, j = 0;
			for (int i = 2; i < x; i++) {
				if (forErato[i - 2]) continue;
				t.add(i);
				l++;
				j = i * 2;
				while (j < x) {
					forErato[j - 2] = true;
					j += i;
				}
			}
			int[] primes = new int[l];
			Iterator<Integer> iterator = t.iterator();
			for (int i = 0; iterator.hasNext(); i++) {
				primes[i] = iterator.next().intValue();
			}
			return primes;
		}

		int rev(int x) {
			int a = 0;
			while (x > 0) {
				a = a * 10 + x % 10;
				x /= 10;
			}
			return a;
		}

		class myDate {
			int d, m, y;

			int[] ml = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

			public myDate(int da, int ma, int ya) {
				d = da;
				m = ma;
				y = ya;
				if ((ma > 12 || ma < 1 || da > ml[ma - 1] || da < 1) && !(d == 29 && m == 2 && y % 4 == 0)) {
					d = 1;
					m = 1;
					y = 9999999;
				}
			}

			void incYear(int x) {
				for (int i = 0; i < x; i++) {
					y++;
					if (m == 2 && d == 29) {
						m = 3;
						d = 1;
						return;
					}
					if (m == 3 && d == 1) {
						if (((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0)) {
							m = 2;
							d = 29;
						}
						return;
					}
				}
			}

			boolean less(myDate x) {
				if (y < x.y) return true;
				if (y > x.y) return false;
				if (m < x.m) return true;
				if (m > x.m) return false;
				if (d < x.d) return true;
				if (d > x.d) return false;
				return true;
			}

			void inc() {
				if ((d == 31) && (m == 12)) {
					y++;
					d = 1;
					m = 1;
				} else {
					if (((y % 4 == 0) && (y % 100 != 0)) || (y % 400 == 0)) {
						ml[1] = 29;
					}
					if (d == ml[m - 1]) {
						m++;
						d = 1;
					} else
						d++;
				}
			}
		}

		int partition(int n, int l, int m) {// n - sum, l - length, m - every
											// part
			// <= m
			if (n < l) return 0;
			if (n < l + 2) return 1;
			if (l == 1) return 1;
			int c = 0;
			for (int i = Math.min(n - l + 1, m); i >= (n + l - 1) / l; i--) {
				c += partition(n - i, l - 1, i);
			}
			return c;
		}

		int rifmQuality(String a, String b) {
			if (a.length() > b.length()) {
				String c = a;
				a = b;
				b = c;
			}
			int c = 0, d = b.length() - a.length();
			for (int i = a.length() - 1; i >= 0; i--) {
				if (a.charAt(i) == b.charAt(i + d)) c++;
				else
					break;
			}
			return c;
		}

		String numSym = "0123456789ABCDEF";

		String ZFromXToYNotation(int x, int y, String z) {
			if (z.equals("0")) return "0";
			String a = "";
			// long q = 0, t = 1;
			BigInteger q = BigInteger.ZERO, t = BigInteger.ONE;
			for (int i = z.length() - 1; i >= 0; i--) {
				q = q.add(t.multiply(BigInteger.valueOf(z.charAt(i) - 48)));
				t = t.multiply(BigInteger.valueOf(x));
			}
			while (q.compareTo(BigInteger.ZERO) == 1) {
				a = numSym.charAt((int) (q.mod(BigInteger.valueOf(y)).intValue())) + a;
				q = q.divide(BigInteger.valueOf(y));
			}
			return a;
		}

		double angleFromXY(int x, int y) {
			if ((x == 0) && (y > 0)) return Math.PI / 2;
			if ((x == 0) && (y < 0)) return -Math.PI / 2;
			if ((y == 0) && (x > 0)) return 0;
			if ((y == 0) && (x < 0)) return Math.PI;
			if (x > 0) return Math.atan((double) y / x);
			else {
				if (y > 0) return Math.atan((double) y / x) + Math.PI;
				else
					return Math.atan((double) y / x) - Math.PI;
			}
		}

		static boolean isNumber(String x) {
			try {
				Integer.parseInt(x);
			} catch (NumberFormatException ex) {
				return false;
			}
			return true;
		}

		static boolean stringContainsOf(String x, String c) {
			for (int i = 0; i < x.length(); i++) {
				if (c.indexOf(x.charAt(i)) == -1) return false;
			}
			return true;
		}

		long pow(long a, long n) { // b > 0
			if (n == 0) return 1;
			long k = n, b = 1, c = a;
			while (k != 0) {
				if (k % 2 == 0) {
					k /= 2;
					c *= c;
				} else {
					k--;
					b *= c;
				}
			}
			return b;
		}

		int pow(int a, int n) { // b > 0
			if (n == 0) return 1;
			int k = n, b = 1, c = a;
			while (k != 0) {
				if (k % 2 == 0) {
					k /= 2;
					c *= c;
				} else {
					k--;
					b *= c;
				}
			}
			return b;
		}

		double pow(double a, int n) { // b > 0
			if (n == 0) return 1;
			double k = n, b = 1, c = a;
			while (k != 0) {
				if (k % 2 == 0) {
					k /= 2;
					c *= c;
				} else {
					k--;
					b *= c;
				}
			}
			return b;
		}

		double log2(double x) {
			return Math.log(x) / Math.log(2);
		}

		int lpd(int[] primes, int x) {// least prime divisor
			int i;
			for (i = 0; primes[i] <= x / 2; i++) {
				if (x % primes[i] == 0) {
					return primes[i];
				}
			}
			;
			return x;
		}

		int np(int[] primes, int x) {// number of prime number
			for (int i = 0; true; i++) {
				if (primes[i] == x) return i;
			}
		}

		int[] dijkstra(int[][] map, int n, int s) {
			int[] p = new int[n];
			boolean[] b = new boolean[n];
			Arrays.fill(p, Integer.MAX_VALUE);
			p[s] = 0;
			b[s] = true;
			for (int i = 0; i < n; i++) {
				if (i != s) p[i] = map[s][i];
			}
			while (true) {
				int m = Integer.MAX_VALUE, mi = -1;
				for (int i = 0; i < n; i++) {
					if (!b[i] && (p[i] < m)) {
						mi = i;
						m = p[i];
					}
				}
				if (mi == -1) break;
				b[mi] = true;
				for (int i = 0; i < n; i++)
					if (p[mi] + map[mi][i] < p[i]) p[i] = p[mi] + map[mi][i];
			}
			return p;
		}

		boolean isLatinChar(char x) {
			if (((x >= 'a') && (x <= 'z')) || ((x >= 'A') && (x <= 'Z'))) return true;
			else
				return false;
		}

		boolean isBigLatinChar(char x) {
			if (x >= 'A' && x <= 'Z') return true;
			else
				return false;
		}

		boolean isSmallLatinChar(char x) {
			if (x >= 'a' && x <= 'z') return true;
			else
				return false;
		}

		boolean isDigitChar(char x) {
			if (x >= '0' && x <= '9') return true;
			else
				return false;
		}

		class NotANumberException extends Exception {
			private static final long serialVersionUID = 1L;
			String mistake;

			NotANumberException() {
				mistake = "Unknown.";
			}

			NotANumberException(String message) {
				mistake = message;
			}
		}

		class Real {
			String num = "0";
			long exp = 0;
			boolean pos = true;

			long length() {
				return num.length();
			}

			void check(String x) throws NotANumberException {
				if (!stringContainsOf(x, "0123456789+-.eE")) throw new NotANumberException("Illegal character.");
				long j = 0;
				for (long i = 0; i < x.length(); i++) {
					if ((x.charAt((int) i) == '-') || (x.charAt((int) i) == '+')) {
						if (j == 0) j = 1;
						else
							if (j == 5) j = 6;
							else
								throw new NotANumberException("Unexpected sign.");
					} else
						if ("0123456789".indexOf(x.charAt((int) i)) != -1) {
							if (j == 0) j = 2;
							else
								if (j == 1) j = 2;
								else
									if (j == 2)
									;
									else
										if (j == 3) j = 4;
										else
											if (j == 4)
											;
											else
												if (j == 5) j = 6;
												else
													if (j == 6)
													;
													else
														throw new NotANumberException("Unexpected digit.");
						} else
							if (x.charAt((int) i) == '.') {
								if (j == 0) j = 3;
								else
									if (j == 1) j = 3;
									else
										if (j == 2) j = 3;
										else
											throw new NotANumberException("Unexpected dot.");
							} else
								if ((x.charAt((int) i) == 'e') || (x.charAt((int) i) == 'E')) {
									if (j == 2) j = 5;
									else
										if (j == 4) j = 5;
										else
											throw new NotANumberException("Unexpected exponent.");
								} else
									throw new NotANumberException("O_o.");
				}
				if ((j == 0) || (j == 1) || (j == 3) || (j == 5)) throw new NotANumberException("Unexpected end.");
			}

			public Real(String x) throws NotANumberException {
				check(x);
				if (x.charAt(0) == '-') pos = false;
				long j = 0;
				String e = "";
				boolean epos = true;
				for (long i = 0; i < x.length(); i++) {
					if ("0123456789".indexOf(x.charAt((int) i)) != -1) {
						if (j == 0) num += x.charAt((int) i);
						if (j == 1) {
							num += x.charAt((int) i);
							exp--;
						}
						if (j == 2) e += x.charAt((int) i);
					}
					if (x.charAt((int) i) == '.') {
						if (j == 0) j = 1;
					}
					if ((x.charAt((int) i) == 'e') || (x.charAt((int) i) == 'E')) {
						j = 2;
						if (x.charAt((int) (i + 1)) == '-') epos = false;
					}
				}
				while ((num.length() > 1) && (num.charAt(0) == '0'))
					num = num.substring(1);
				while ((num.length() > 1) && (num.charAt(num.length() - 1) == '0')) {
					num = num.substring(0, num.length() - 1);
					exp++;
				}
				if (num.equals("0")) {
					exp = 0;
					pos = true;
					return;
				}
				while ((e.length() > 1) && (e.charAt(0) == '0'))
					e = e.substring(1);
				try {
					if (e != "") if (epos) exp += Long.parseLong(e);
					else
						exp -= Long.parseLong(e);
				} catch (NumberFormatException exc) {
					if (!epos) {
						num = "0";
						exp = 0;
						pos = true;
					} else {
						throw new NotANumberException("Too long exponent");
					}
				}
			}

			public Real() {
			}

			String toString(long mantissa) {
				String a = "", b = "";
				if (exp >= 0) {
					a = num;
					if (!pos) a = '-' + a;
					for (long i = 0; i < exp; i++)
						a += '0';
					for (long i = 0; i < mantissa; i++)
						b += '0';
					if (mantissa == 0) return a;
					else
						return a + "." + b;
				} else {
					if (exp + length() <= 0) {
						a = "0";
						if (mantissa == 0) {
							return a;
						}
						if (mantissa < -(exp + length() - 1)) {
							for (long i = 0; i < mantissa; i++)
								b += '0';
							return a + "." + b;
						} else {
							if (!pos) a = '-' + a;
							for (long i = 0; i < mantissa; i++)
								if (i < -(exp + length())) b += '0';
								else
									if (i + exp >= 0) b += '0';
									else
										b += num.charAt((int) (i + exp + length()));
							return a + "." + b;
						}
					} else {
						if (!pos) a = "-";
						for (long i = 0; i < exp + length(); i++)
							a += num.charAt((int) i);
						if (mantissa == 0) return a;
						for (long i = exp + length(); i < exp + length() + mantissa; i++)
							if (i < length()) b += num.charAt((int) i);
							else
								b += '0';
						return a + "." + b;
					}
				}
			}
		}

		boolean containsRepeats(int... num) {
			Set<Integer> s = new TreeSet<Integer>();
			for (int d : num)
				if (!s.contains(d)) s.add(d);
				else
					return true;
			return false;
		}

		int[] rotateDice(int[] a, int n) {
			int[] c = new int[6];
			if (n == 0) {
				c[0] = a[1];
				c[1] = a[5];
				c[2] = a[2];
				c[3] = a[0];
				c[4] = a[4];
				c[5] = a[3];
			}
			if (n == 1) {
				c[0] = a[2];
				c[1] = a[1];
				c[2] = a[5];
				c[3] = a[3];
				c[4] = a[0];
				c[5] = a[4];
			}
			if (n == 2) {
				c[0] = a[3];
				c[1] = a[0];
				c[2] = a[2];
				c[3] = a[5];
				c[4] = a[4];
				c[5] = a[1];
			}
			if (n == 3) {
				c[0] = a[4];
				c[1] = a[1];
				c[2] = a[0];
				c[3] = a[3];
				c[4] = a[5];
				c[5] = a[2];
			}
			if (n == 4) {
				c[0] = a[0];
				c[1] = a[2];
				c[2] = a[3];
				c[3] = a[4];
				c[4] = a[1];
				c[5] = a[5];
			}
			if (n == 5) {
				c[0] = a[0];
				c[1] = a[4];
				c[2] = a[1];
				c[3] = a[2];
				c[4] = a[3];
				c[5] = a[5];
			}
			return c;
		}

		int min(int... a) {
			int c = Integer.MAX_VALUE;
			for (int d : a)
				if (d < c) c = d;
			return c;
		}

		int max(int... a) {
			int c = Integer.MIN_VALUE;
			for (int d : a)
				if (d > c) c = d;
			return c;
		}

		int[] normalizeDice(int[] a) {
			int[] c = a.clone();
			if (c[0] != 0) if (c[1] == 0) c = rotateDice(c, 0);
			else
				if (c[2] == 0) c = rotateDice(c, 1);
				else
					if (c[3] == 0) c = rotateDice(c, 2);
					else
						if (c[4] == 0) c = rotateDice(c, 3);
						else
							if (c[5] == 0) c = rotateDice(rotateDice(c, 0), 0);
			while (c[1] != min(c[1], c[2], c[3], c[4]))
				c = rotateDice(c, 4);
			return c;
		}

		boolean sameDice(int[] a, int[] b) {
			for (int i = 0; i < 6; i++)
				if (a[i] != b[i]) return false;
			return true;
		}

		final double goldenRatio = (1 + Math.sqrt(5)) / 2;
		final double aGoldenRatio = (1 - Math.sqrt(5)) / 2;

		long Fib(int n) {
			if (n < 0) if (n % 2 == 0) return -Math.round((pow(goldenRatio, -n) - pow(aGoldenRatio, -n)) / Math.sqrt(5));
			else
				return -Math.round((pow(goldenRatio, -n) - pow(aGoldenRatio, -n)) / Math.sqrt(5));
			return Math.round((pow(goldenRatio, n) - pow(aGoldenRatio, n)) / Math.sqrt(5));
		}

		class japaneeseComparator implements Comparator<String> {
			@Override
			public int compare(String a, String b) {
				int ai = 0, bi = 0;
				boolean m = false, ns = false;
				if (a.charAt(ai) <= '9' && a.charAt(ai) >= '0') {
					if (b.charAt(bi) <= '9' && b.charAt(bi) >= '0') m = true;
					else
						return -1;
				}
				if (b.charAt(bi) <= '9' && b.charAt(bi) >= '0') {
					if (a.charAt(ai) <= '9' && a.charAt(ai) >= '0') m = true;
					else
						return 1;
				}
				a += "!";
				b += "!";
				int na = 0, nb = 0;
				while (true) {
					if (a.charAt(ai) == '!') {
						if (b.charAt(bi) == '!') break;
						return -1;
					}
					if (b.charAt(bi) == '!') {
						return 1;
					}
					if (m) {
						int ab = -1, bb = -1;
						while (a.charAt(ai) <= '9' && a.charAt(ai) >= '0') {
							if (ab == -1) ab = ai;
							ai++;
						}
						while (b.charAt(bi) <= '9' && b.charAt(bi) >= '0') {
							if (bb == -1) bb = bi;
							bi++;
						}
						m = !m;
						if (ab == -1) {
							if (bb == -1) continue;
							else
								return 1;
						}
						if (bb == -1) return -1;
						while (a.charAt(ab) == '0' && ab + 1 != ai) {
							ab++;
							if (!ns) na++;
						}
						while (b.charAt(bb) == '0' && bb + 1 != bi) {
							bb++;
							if (!ns) nb++;
						}
						if (na != nb) ns = true;
						if (ai - ab < bi - bb) return -1;
						if (ai - ab > bi - bb) return 1;
						for (int i = 0; i < ai - ab; i++) {
							if (a.charAt(ab + i) < b.charAt(bb + i)) return -1;
							if (a.charAt(ab + i) > b.charAt(bb + i)) return 1;
						}
					} else {
						m = !m;
						while (true) {
							if (a.charAt(ai) <= 'z' && a.charAt(ai) >= 'a' && b.charAt(bi) <= 'z' && b.charAt(bi) >= 'a') {
								if (a.charAt(ai) < b.charAt(bi)) return -1;
								if (a.charAt(ai) > b.charAt(bi)) return 1;
								ai++;
								bi++;
							} else
								if (a.charAt(ai) <= 'z' && a.charAt(ai) >= 'a') return 1;
								else
									if (b.charAt(bi) <= 'z' && b.charAt(bi) >= 'a') return -1;
									else
										break;
						}
					}
				}
				if (na < nb) return 1;
				if (na > nb) return -1;
				return 0;
			}
		}

		Random random = new Random();
	}

	void readIntArray(int[] a) throws IOException {
		for (int i = 0; i < a.length; i++) a[i] = nextInt();
	}
	
	String readChars(int l) throws IOException {
		String r = "";
		for (int i = 0; i < l; i++) r += (char)br.read();
		return r;
	}

	StreamTokenizer in;
	PrintWriter out;
	boolean oj;
	BufferedReader br;

	void init() throws IOException {
		oj = System.getProperty("ONLINE_JUDGE") != null;
		Reader reader = oj ? new InputStreamReader(System.in) : new FileReader("input.txt");
		Writer writer = oj ? new OutputStreamWriter(System.out) : new FileWriter("output.txt");
		br = new BufferedReader(reader);
		in = new StreamTokenizer(br);
		out = new PrintWriter(writer);
	}

	long selectionTime = 0;

	void startSelection() {
		selectionTime -= System.currentTimeMillis();
	}

	void stopSelection() {
		selectionTime += System.currentTimeMillis();
	}

	void run() throws IOException {
		long beginTime = System.currentTimeMillis();
		long beginMem = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
		init();
		solve();
		long endMem = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
		long endTime = System.currentTimeMillis();
		if (!oj) {
			System.out.println("Memory used = " + (endMem - beginMem));
			System.out.println("Total memory = " + (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()));
			System.out.println("Running time = " + (endTime - beginTime));
		}
		out.flush();
	}

	int nextInt() throws IOException {
		in.nextToken();
		return (int) in.nval;
	}

	long nextLong() throws IOException {
		in.nextToken();
		return (long) in.nval;
	}

	String nextString() throws IOException {
		in.nextToken();
		return in.sval;
	}

	double nextDouble() throws IOException {
		in.nextToken();
		return in.nval;
	}

	myLib lib = new myLib();

	/*
	 * class cubeWithLetters { String consts = "ЧКТФЭЦ"; char[][] letters = { {
	 * 'А', 'Б', 'Г', 'В' }, { 'Д', 'Е', 'З', 'Ж' }, { 'И', 'Л', 'Н', 'М' }, {
	 * 'О', 'П', 'С', 'Р' }, { 'У', 'Х', 'Щ', 'Ш' }, { 'Ы', 'Ь', 'Я', 'Ю' } };
	 * 
	 * char get(char x) { if (consts.indexOf(x) != -1) return x; for (int i = 0;
	 * i < 7; i++) { for (int j = 0; j < 4; j++) { if (letters[i][j] == x) { if
	 * (j == 0) return letters[i][3]; else return letters[i][j - 1]; } } }
	 * return '!'; }
	 * 
	 * void subrotate(int x) { char t = letters[x][0]; letters[x][0] =
	 * letters[x][3]; letters[x][3] = letters[x][2]; letters[x][2] =
	 * letters[x][1]; letters[x][1] = t; }
	 * 
	 * void rotate(int x) { subrotate(x); char t; if (x == 0) { t =
	 * letters[1][0]; letters[1][0] = letters[2][0]; letters[2][0] =
	 * letters[3][0]; letters[3][0] = letters[5][2]; letters[5][2] = t;
	 * 
	 * t = letters[1][1]; letters[1][1] = letters[2][1]; letters[2][1] =
	 * letters[3][1]; letters[3][1] = letters[5][3]; letters[5][3] = t; } if (x
	 * == 1) { t = letters[2][0]; letters[2][0] = letters[0][0]; letters[0][0] =
	 * letters[5][0]; letters[5][0] = letters[4][0]; letters[4][0] = t;
	 * 
	 * t = letters[2][3]; letters[2][3] = letters[0][3]; letters[0][3] =
	 * letters[5][3]; letters[5][3] = letters[4][3]; letters[4][3] = t; } if (x
	 * == 2) { t = letters[0][3]; letters[0][3] = letters[1][2]; letters[1][2] =
	 * letters[4][1]; letters[4][1] = letters[3][0]; letters[3][0] = t;
	 * 
	 * t = letters[0][2]; letters[0][2] = letters[1][1]; letters[1][1] =
	 * letters[4][0]; letters[4][0] = letters[3][3]; letters[3][3] = t; } if (x
	 * == 3) { t = letters[2][1]; letters[2][1] = letters[4][1]; letters[4][1] =
	 * letters[5][1]; letters[5][1] = letters[0][1]; letters[0][1] = t;
	 * 
	 * t = letters[2][2]; letters[2][2] = letters[4][2]; letters[4][2] =
	 * letters[5][2]; letters[5][2] = letters[0][2]; letters[0][2] = t; } if (x
	 * == 4) { t = letters[2][3]; letters[2][3] = letters[1][3]; letters[1][3] =
	 * letters[5][1]; letters[5][1] = letters[3][3]; letters[3][3] = t;
	 * 
	 * t = letters[2][2]; letters[2][2] = letters[1][2]; letters[1][2] =
	 * letters[5][0]; letters[5][0] = letters[3][2]; letters[3][2] = t; } if (x
	 * == 5) { t = letters[4][3]; letters[4][3] = letters[1][0]; letters[1][0] =
	 * letters[0][1]; letters[0][1] = letters[3][2]; letters[3][2] = t;
	 * 
	 * t = letters[4][2]; letters[4][2] = letters[1][3]; letters[1][3] =
	 * letters[0][0]; letters[0][0] = letters[3][1]; letters[3][1] = t; } }
	 * 
	 * public String toString(){ return "  " + letters[0][0] + letters[0][1] +
	 * "\n" + "  " + letters[0][3] + letters[0][2] + "\n" + letters[1][0] +
	 * letters[1][1] + letters[2][0] + letters[2][1] + letters[3][0] +
	 * letters[3][1] + "\n" + letters[1][3] + letters[1][2] + letters[2][3] +
	 * letters[2][2] + letters[3][3] + letters[3][2] + "\n" + "  " +
	 * letters[4][0] + letters[4][1] + "\n" + "  " + letters[4][3] +
	 * letters[4][2] + "\n" + "  " + letters[5][0] + letters[5][1] + "\n" + "  "
	 * + letters[5][3] + letters[5][2] + "\n"; } }
	 */
	
	Vector<Integer>[] a;
	int n, mc, c1, c2;
	int[] col;
	
	void wave(int x, int p) {
		for (Iterator<Integer> i = a[x].iterator(); i.hasNext(); ) {
			int t = i.next();
			if (t == x || t == p) continue;
			if (col[t] == 0) {
				col[t] = mc;
				wave(t, x);
			} else {
				c1 = x;
				c2 = t;
			}
		}
	}

	void solve() throws IOException {
		/*
		 * String s = "ЕПОЕЬРИТСГХЖЗТЯПСТАПДСБИСТЧК"; //String s =
		 * "ЗЬУОЫТВЗТЯПУБОЫТЕАЫШХЯАТЧК"; cubeWithLetters cube = new
		 * cubeWithLetters(); for (int x = 0; x < 4; x++) { for (int y = x + 1;
		 * y < 5; y++) { for (int z = y + 1; z < 6; z++) { cube = new
		 * cubeWithLetters(); out.println(cube.toString()); cube.rotate(x);
		 * out.println(cube.toString()); cube.rotate(y);
		 * out.println(cube.toString()); cube.rotate(z);
		 * out.println(cube.toString()); out.print(x + " " + y + " " + z +
		 * " = "); for (int i = 0; i < s.length(); i++) {
		 * out.print(cube.get(s.charAt(i))); } out.println(); } } }
		 */

		n = nextInt();
		a = new Vector[n];
		for (int i = 0; i < n; i++) a[i] = new Vector<Integer>();
		for (int i = 0; i < n - 1; i++) {
			int t1 = nextInt() - 1, t2 = nextInt() - 1;
			a[t1].add(t2);
			a[t2].add(t1);
		}
		col = new int[n];
		int s = 0;
		String mes = "";
		while (true) {
			mc = 0;
			Arrays.fill(col, 0);
			for (int i = 0; i < n; i++) {
				if (col[i] == 0) {
					mc++;
					col[i] = mc;
					wave(i, -1);
				}
			}
			if (mc == 1) break;
			s++;
			mes += (c1 + 1) + " " + (c2 + 1) + " " + (c1 + 1) + " ";
			for (int i = 0; i < n; i++) {
				if (col[i] != col[c1]) {
					mes += (i + 1) + "\n";
					a[c1].removeElement(c2);
					a[c2].removeElement(c1);
					a[c1].add(i);
					a[i].add(c1);
					break;
				}
			}
		}
		out.println(s);
		out.print(mes);
	}
}