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:
import java.util.*;
import java.io.*;
 
public class AiseHi {
	static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 

        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 

        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 

        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 

        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 

        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 

        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }
	static int par[] = new int[10000];
	static int size[] = new int[10000];
	public static void main (String[] args) {
		FastReader sc = new FastReader();
		PrintWriter out = new PrintWriter(System.out);
		int t = 1;
//    	t = sc.nextInt();
    	while(t-->0) {
    		 int n = sc.nextInt();
    		 for(int i=1;i<=n;i++) {
    			 par[i] = i;
    			 size[i] = 1;
    		 }
    		 List<pair> l = new ArrayList<>();
    		 for(int i=1;i<n;i++) {
    			 int u = sc.nextInt();
    			 int v = sc.nextInt();
    			 int pu = findPar(u);
    			 int pv = findPar(v);
    			 if(pu != pv) {
    				 if(size[pu]>size[pv]) {
    					 par[pv] = pu;
    					 size[pu] += size[pv];
    				 }
    				 else {
    					 par[pu] = pv;
    					 size[pv] += size[pu];
    				 }
    			 }
    			 else {
    				 l.add(new pair(u,v));
    			 }
    		 }
    		 Set<Integer> s = new HashSet<>();
    		 for(int i=1;i<=n;i++) {
    			 int parent = findPar(i);
    			 s.add(parent);
    		 }
    		 List<Integer> a = new ArrayList<>();
    		 a.addAll(s);
    		 out.write(a.size()-1+"\n");
    		 for(int i=0;i<a.size()-1;i++) {
    			 out.write(l.get(i).a+" "+l.get(i).b+" "+a.get(i)+" "+a.get(i+1)+"\n");
    		 }
		out.close();
    	}
	}
	private static int findPar(int x) {
		if(x == par[x]) return x;
		
		return par[x] = findPar(par[x]);
	}
	static long findl(long[] a, int l, int h, long val, long k) {
		int ans = -1;
		while(l<=h) {
			int mid = (l+h)/2;
			if(a[mid] - val<=k) {
				ans = mid;
				l = mid + 1;
			}
			else h = mid-1;
		}
		return ans==-1?0:ans;
	}
	static long findh(long[] a, int l, int h, long val, long k) {
		int ans = -1;
		while(l<=h) {
			int mid = (l+h)/2;
			if(val - a[mid]<=k) {
				ans = mid;
				h = mid - 1;
			}
			else l = mid+1;
		}
		return ans==-1?0:ans;
	}
	
	private static int ub(List<Long> list, long l) {
		int lo = 0,h = list.size()-1;
		int ans = -1;
		while(lo<=h) {
			int mid = lo+(h-lo)/2;
			if(list.get(mid)<=l) {
				lo = mid+1;
				ans = mid;
			}
			else {
				
				h = mid-1;
			}
		}
		
		return ans+1;
	}
	private static long lb(List<Long> list, long l) {
		int lo = 0,h = list.size()-1;
		int ans = -1;
		while(lo<=h) {
			int mid = lo+(h-lo)/2;
			if(list.get(mid)<=l) {
				if(mid>0 && list.get(mid-1)==l) h = mid - 1;
				else {
					lo = mid+1;
					ans = mid;
				}
			}
			else {
				h = mid-1;
			}
		}
		if(list.get(ans)==l) return ans;
		return ans+1;
	}
	private static void swap(int[] a, int i, int j) {
		int temp = a[i];
		a[i] = a[j];
		a[j] = temp;
	}
	static long lstbt(long val) {
		long msk = val & (val-1);
		return (long) (Math.log(val^msk)/Math.log(2));
	}
	private static long sqrt(long x) {
		long l = 1,h = x;
		long ans = 0;
		while(l<=h) {
			long mid = (l+(h-l)/2);
			if(mid>x/mid) h = mid-1;
			else {
				ans = mid;
				l = mid+1;
			}
		}
		return ans;
	}
	static boolean prime[] = new boolean[10000001];
	static void sieve() {
		prime[0] = true;
		prime[1] = true;
		int max = 10000000;
		for(int i=2;i*i<=max;i++) {
			if(!prime[i]) {
				for(int j=i*i;j<=max;j+=i)
					prime[j] = true;
			}
		}
	}
	static String reverse(String x) {
		StringBuilder input1 = new StringBuilder();
		
        input1.append(x);
        
        input1 = input1.reverse();
        
        return input1.toString();
	}
	static int gcd(int val, int g) {
 
		if(g==0) return val;
		
		return gcd(g,val%g);
	}
	static int lcm(int a,int b) {
		return (a*b)/gcd(a,b);
	}
}
class pair implements Comparable<pair>{
	int a;
	int b;
	pair(int a,int b){
		this.a = a;
		this.b = b;
	}
	@Override
	public int compareTo(pair o) {
		return (int) (this.a - o.a);
	}
}