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:

//package cf;
import java.io.*;
import java.util.*;
import java.util.jar.JarOutputStream;

public class T_class {
    static int p=1000000007;
    static int max=(int)1e5;
    static List<Integer> l1=new ArrayList<>();
    static boolean prime[]=new boolean[max];
    static long fact[]=new long[3_000_00];
    static class  pr_int
    {
        int first;
        int second;
        public pr_int(int first, int second) {
            this.first = first;
            this.second = second;
        }
    }
    static  class edge
    {
        int v,w,lst;
        edge(int v,int w)
        {
            this.v=v;
            this.w=w;
        }
    }
    static  class wt
    {
        int n,d,s;

        public wt(int n, int d, int s) {
            this.n = n;
            this.d = d;
            this.s = s;
        }
    }
    static  long anss=0;
    public static void main(String[] args) throws Exception {
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(java.io.FileDescriptor.out), "ASCII"), 512);
        FastReader sc = new FastReader();
        int t =1;//sc.nextInt();
        StringBuilder sb2 = new StringBuilder();
        while (t-- >0)
        {

            int n=sc.nextInt();
            int p[]=new int[n+1];
            int r[]=new int[n+1];

            edge ar[]=new edge[n+1];
            for(int i=0;i<=n;i++)
            {
                p[i]=i;
                r[i]=1;
            }
            ArrayList<edge> dq=new ArrayList<>();
            Set<Integer> set=new HashSet<>();
            int fst=-1;
            for(int i=0;i<n-1;i++)
            {
                ar[i]=new edge(sc.nextInt()-1,sc.nextInt()-1);
                if(union(ar[i].v,ar[i].w,p,r))
                {
                    dq.add(new edge(ar[i].v,ar[i].w));
                }
            }
            ArrayDeque<Integer> l1=new ArrayDeque<>();
            for(int i=0;i<n;i++)
            {
                int find=find(i,p,r);
                if(fst==-1||find==fst)
                {
                    fst=find;
                }
                else
                set.add(find);

//                System.out.println(find);
            }
            l1.addAll(set);
  //          System.out.println(l1);
            ArrayDeque<String> res=new ArrayDeque<>();
            for(int i=0;i<dq.size();i++)
            {
                edge cur=dq.get(i);
                int i1=cur.v+1;
                int j1=cur.w+1;
                int x=l1.pollFirst()+1;
                int y=fst+1;
                res.addLast(i1+" "+j1+" "+x+" "+y);
            }
            System.out.println(dq.size());
        while (!res.isEmpty())
        {
            System.out.println(res.pollFirst());
        }
        }
        System.out.println(sb2.toString());
        out.flush();

    }
    static void sortMyMapusingValues(HashMap<Integer, Integer> hm) {
        List<Map.Entry<Integer, Integer>> capitalList = new LinkedList<>(hm.entrySet());

        Collections.sort(capitalList, new Comparator<Map.Entry<Integer, Integer>>() {
            public int compare(Map.Entry<Integer, Integer> o1, Map.Entry<Integer, Integer> o2) {
                return (o1.getValue()).compareTo(o2.getValue());
            }
        });
        HashMap<Integer, Integer> result = new HashMap<>();
        for (Map.Entry<Integer, Integer> entry : capitalList) {
            result.put(entry.getKey(), entry.getValue());
        }
    }
    static class BIT {
        long[] tree;
        public BIT(int size) {
            tree = new long[size + 1];
        }
        public long sum(int i) {
            long ans = 0;
            while (i > 0) {
                ans += tree[i];
                i -= i & -i;
            }
            return ans;
        }

        public long query(int i, int j) {
            return sum(j) - sum(i - 1);
        }

        public void add(int i, long val) {
            while (i < tree.length) {
                tree[i] += val;
                i += i & -i;
            }
        }

        public void set(int i, long val) {
            add(i, val - query(i, i));
        }
    }

    static long lcm(long a,long b)
    {
        return  a*b/gcd(a,b);
    }
    static boolean done=false;
    static long ret;
    public  static long tolong(char ar[])
    {
        long ans=0;
        for(char i:ar)
            ans=ans*10+ (i-'0');

        return ans;
    }
    public  static  void recur(char ar[],int n,int cur,long lcm,boolean con)
    {
        if(cur==n)
        {
            System.out.println(tolong(ar)+" "+lcm);
            done=tolong(ar)%lcm==0;
            if(done)
                ret=tolong(ar);
            return;
        }
        int lst=ar[cur]-'0';
        for(int i=con?ar[cur]-'0':0;i<=9;i++)
        {
            char prev=ar[cur];
            ar[cur]=(char) (i+'0');
            recur(ar, n, cur + 1, i==0?lcm:lcm(i,lcm),lst==i);
            ar[cur]=prev;
            if(done)
                return ;
        }
    }
    static long ansa(long l,long r,long s,long ss,int n,int ar[])
    {

        while(l<=r)
        {
            long mid=(l+r)/2;
            long tot=0;
            for(int i=0;i<n;i++)
            {
                tot+=Math.abs(ar[i]-mid);
            }

            if(tot*2<=s)
            {
                // System.out.println(s+" - "+(mid*n)+" <= "+ss);
                return mid;
            }
            else if(tot*2>s)
            {
                r=mid-1;
            }
            else
            {
                l=mid+1;
            }
        }
        return 1;
    }
    static void ruffle_sort(long[] a) {
        //shandom_ruffle
        Random r=new Random();
        int n=a.length;
        for (int i=0; i<n; i++) {
            int oi=Math.abs(r.nextInt(i+1));
            long temp=a[i];
            a[i]=a[oi];
            a[oi]=temp;
        }

        //sort
        Arrays.sort(a);
    }
    static void ruffle_sort(int[] a) {
        //shandom_ruffle
        Random r=new Random();
        int n=a.length;
        for (int i=0; i<n; i++) {
            int oi=Math.abs(r.nextInt(i+1));
            int temp=a[i];
            a[i]=a[oi];
            a[oi]=temp;
        }

        //sort
        Arrays.sort(a);
    }
    static long mod=(long) 1e9+7;
    private static long nC2(long n) {
        return n*(n-1)/2;
    }
    static long mul(long a, long b) {
        return a*b%mod;
    }

    static long add(long a, long b) {
        return (a+b)%mod;
    }
    static void precomp() {
        fact[0]=1;
        for (int i=1; i<fact.length; i++) fact[i]=mul(fact[i-1], i);
    }
    static long modInv(long x) {
        return pow(x, mod-2,mod);
    }
    static long nCk(int n, int k) {
        return mul(fact[n], mul(modInv(fact[k]), modInv(fact[n-k])));
    }


    private static List<Long> getdivisors(long n) {
        List<Long> l1=new ArrayList<>();
        for(long i=1;i<=Math.sqrt(n);i++)
        {
            if(n%i==0){
                l1.add(i);
                if(n/i!=i)
                    l1.add(n/i);
            }
        }
        // System.out.println(l1);
        Collections.sort(l1);
        return l1;
    }

    private static int count(int k, int l, String cur) {
        char ar[]=cur.toCharArray();
        int c=0;
        for(int i=k;i<=l;i++)
        {
            if(i=='1')
                c++;
        }
        return c;
    }

    private static String revese(String substring) {
        StringBuilder sb=new StringBuilder();
        sb.append(substring);
        sb=sb.reverse();
        return sb.toString();
    }


    static  int ht[]=new int[max];
    /*static class BIT {
        long[] tree;
        public BIT(int size) {
            tree = new long[size + 1];
        }
        public long sum(int i) {
            long ans = 0;
            while (i > 0) {
                ans += tree[i];
                i -= i & -i;
            }
            return ans;
        }

        public long query(int i, int j) {
            return sum(j) - sum(i - 1);
        }

        public void add(int i, long val) {
            while (i < tree.length) {
                tree[i] += val;
                i += i & -i;
            }
        }

        public void set(int i, long val) {
            add(i, val - query(i, i));
        }
    }
    */public static long pow(long a,long b,long m)
    {
        long r=1;
        while(b!=1)
        {
            if(b%2!=0)
                r=(r*a)%m;
            b=b>>1;
            a=(a*a)%m;
        }
        return (r*a)%m;
    }
    /*public static long gcd(long a,long b)
    {
        if(b>a)
        {
            a=a^b;
            b=a^b;
            a=a^b;
        }
        if(b==0)
            return a;
        return gcd(b,a%b);
    }*/
    static long gcd(long a, long b) {
        if (b == 0)
            return a;
        return gcd(b, a % b);
    }
    public static void extgcd(long a,long b)
    {/*
            if(a==0)
            {
                x=0;
                y=1;
                d=b;
                // return ;
            }
            else
            {

                extgcd(b%a,a);

                long t=y;
                y=x;
                x=t-(b/a)*x;
            }*/
    }
    static  Set<Integer > used=new HashSet<>();
    public static void dfs(List<Integer>[] adj, int u, int p, boolean[] vis,long ind[],long n)
    {
        // anss-=((ind[u]-1)*(ind[u]-2))/2>0&&!used.contains(u)?((ind[u]-1)*(ind[u]-2))/2:0;

        if(((ind[u]-1)*(ind[u]-2))/2>0)
        {
            //   System.out.println(u+" -- "+((ind[u]-1)*(ind[u]))/2);
            //   used.add(u);
        }
        vis[u]=true;
        int c=0;
        for(int v:adj[u])
        {
            if(v!=p&&vis[v])
            {
                //   System.out.println(u+" c--c"+v+" "+((ind[v]-1)*(ind[v]))/2);
                if(((ind[v]-1)*(ind[v]-2))/2>0) {
                    anss -= ((ind[v] - 1) * (ind[v] - 2)) / 2 > 0 && !used.contains(v) ? ((ind[v] - 1) * (ind[v] - 2)) / 2 : 0;
                    used.add(v);
                }
                if(((ind[u]-1)*(ind[u]-2))/2>0) {
                    anss -= ((ind[u] - 1) * (ind[u] - 2)) / 2 > 0 && !used.contains(u) ? ((ind[u] - 1) * (ind[u] - 2)) / 2 : 0;
                    used.add(u);
                }
                continue;
            }
            if(!vis[v])
            {
                c++;
                dfs(adj,v,u, vis,ind,n+1);
            }
        }
        if(c==0)
        {
            anss+=(n)*(n+1l)/2;
        }
        vis[u]=false;
    }
    public static void seive()
    {
        for(int i=0;i<max;i++)
            prime[i] = true;

        for(int p = 2; p*p <=max; p++)
        {
            // If prime[p] is not changed, then it is a prime
            if(prime[p] == true)
            {
                // Update all multiples of p
                for(int i = p*p; i <=max; i += p)
                    prime[i] = false;
            }
        }

        // Print all prime numbers
        for(int i = 2; i <= max; i++)
        {
            if(prime[i] == true)
            {
                l1.add(i);
            }
        }
    }
    static int max_abv=Integer.MIN_VALUE,min_abv=Integer.MAX_VALUE,ans=0;
    public static boolean union(int a, int b, int p[], int r[]){
        // add your code here
        int pa=find(a,p,r);
        int pb=find(b,p,r);
        if(pa==pb)
            return true;
        if(pa!=pb)
        {
            if(r[pa]<r[pb])
            {
                p[pa]=pb;
            }
            else if(r[pa]>r[pb])
            {
//                p[pb]=pa;

                p[pb]=pa;
            }
            else
            {
                p[pa]=pb;

                r[pb]++;
            }
        }
        return false;
    }
    public static int find(int x,int p[],int r[])
    {
        if(p[x]==x)
            return x;
        p[x]=find(p[x],p,r);
        return p[x];
    }
    public static int binary_Search_upper(int[] ar,int l, int x)
    {
        int res=-1;
        int r=ar.length-1;
        while(l<=r)
        {
            int mid=(l+r)>>1;
            if(ar[mid]<=x)
            {
                res=mid;
                l=mid+1;
            }
            else if(ar[mid]>x)
            {
                //res=mid;
                r=mid-1;
            }
        }
        return res;
    }
    public static int binary_Search_lower(long[] ar, long x)
    {
        int res=ar.length;
        int l=0;int r=ar.length-1;
        while(l<=r)
        {
            int mid=(l+r)>>1;
            if(ar[mid]>=x)
            {
                res=mid;
                r=mid-1;
            }
            else
            {
                l=mid+1;
            }
        }
        return res;
    }
    int bit[]=new int[(int)1e6];
    public void update(int n,int val,int i)
    {
        i++;
        while(i<n)
        {
            bit[i]+=val;
            i+=(i)&(-i);
        }

    }
    public long query(int n,int i)
    {
        i++;
        long sum=0;
        while(i>0)
        {
            sum+=bit[i];
            i-=(i)&(-i);
        }
        return sum;
    }


    ///////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    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;
        }
    }


}