Problem: In Berland there are n cities and n - 1 bidirectional roads. Each road connects some pair of cities, from any city you can get to any other one using only the given roads.

In each city there is exactly one repair brigade. To repair some road, you need two teams based in the cities connected by the road to work simultaneously for one day. Both brigades repair one road for the whole day and cannot take part in repairing other roads on that day. But the repair brigade can do nothing on that day.

Determine the minimum number of days needed to repair all the roads. The brigades cannot change the cities where they initially are.

Input

The first line of the input contains a positive integer n (2 ≤ n ≤ 200 000) — the number of cities in Berland.

Each of the next n - 1 lines contains two numbers ui, vi, meaning that the i-th road connects city ui and city vi (1 ≤ ui, vi ≤ n, ui ≠ vi).

Output

First print number k — the minimum number of days needed to repair all the roads in Berland.

In next k lines print the description of the roads that should be repaired on each of the k days. On the i-th line print first number di — the number of roads that should be repaired on the i-th day, and then di space-separated integers — the numbers of the roads that should be repaired on the i-th day. The roads are numbered according to the order in the input, starting from one.

If there are multiple variants, you can print any of them.

Examples

Input

4
1 2
3 4
3 2


Output

2
2 2 1
1 3


Input

6
3 4
5 4
3 2
1 3
4 6


Output

3
1 1 
2 2 3 
2 4 5 

Note

In the first sample you can repair all the roads in two days, for example, if you repair roads 1 and 2 on the first day and road 3 — on the second day.

Solution (in JAVA):

Solution:
import java.io.*;
import java.util.*;
import java.math.*;
import java.math.BigInteger;


public final class C
{    
	static PrintWriter out = new PrintWriter(System.out); 
	static StringBuilder ans=new StringBuilder();
	static FastReader in=new FastReader();
	static ArrayList<ArrayList<edge>> g;
	static long mod=(long)1e9+7,INF=Long.MAX_VALUE;
	static boolean set[],col[]; 
	static int par[],tot[],partial[];
	static int D[],P[][];
	static long dp[][],max=0;
	static long seg[];
	//static pair moves[]= {new pair(-1,0),new pair(1,0), new pair(0,-1), new pair(0,1)};
	public static void main(String args[])throws IOException
	{				
		int N=i();
		int A[]=new int[N+1];
		int B[]=new int[N+1];
		setGraph(N);
		HashMap<Integer,Integer> mp=new HashMap<>();

		int max=0;
		int sc=0;
		for(int i=1; i<N; i++)
		{
			A[i]=i();
			B[i]=i();
			g.get(A[i]).add(new edge(B[i],i));
			g.get(B[i]).add(new edge(A[i],i));
			int f=mp.getOrDefault(A[i], 0)+1;
			mp.put(A[i], f);
			max=Math.max(max,f);
			if(max==f)sc=A[i];
			f=mp.getOrDefault(B[i], 0)+1;
			mp.put(B[i], f);
			if(max==f)sc=A[i];
			max=Math.max(max,f);
		}
		ArrayList<Integer> fin[]=new ArrayList[max];
		for(int i=0; i<max; i++)fin[i]=new ArrayList<Integer>();
		dfs(sc,-1,max,fin);
		for(ArrayList<Integer> a:fin)
		{
			ans.append(a.size()+" ");
			for(int i:a)ans.append(i+" ");
			ans.append("\n");
		}
		
		out.println(max);		
		out.println(ans);
		out.close();
	}
	static void dfs(int N,int p,int D,ArrayList<Integer> A[])
	{
		int d=0;
		for(edge c:g.get(N))
		{
			if(c.a==p)continue;
			if(d==D)d++;
			A[d].add(c.road);
			dfs(c.a,N,d,A);
			d++;
			
		}
	}
	static long f1(long a,long A[],long bits[],long sum)
	{
		long s=A.length;
		s=mul(s,a);
		s=(s+(sum%mod))%mod;
		long p=1L;
		for(long x:bits)
		{
			if((a&p)!=0)s=((s-mul(x,p))+mod)%mod;
			p<<=1;
		}
		return s;
	}
	static long f2(long a,long A[],long bits[])
	{
		long s=0;
		long p=1L;
		for(long x:bits)
		{
			if((a&p)!=0)
			{
				s=(s+mul(p,x))%mod;
			}
			p<<=1;
		}
		return s;
	}
	static long f(long x1,long y1,long x2,long y2)
	{
		return Math.abs(x1-x2)+Math.abs(y1-y2);
	}
	static long f(long x,long max,long s)
	{
		long l=-1,r=(x/s)+1;
		while(r-l>1)
		{
			long m=(l+r)/2;
			if(x-m*s>max)l=m;
			else r=m;
		}
		return l+1;
	}
	static int f(long A[],long x)
	{
		int l=-1,r=A.length;
		while(r-l>1)
		{
			int m=(l+r)/2;
			if(A[m]>=x)r=m;
			else l=m;			
		}
		return r;
	}
	static void build(int v,int tl,int tr,long A[])
	{
		if(tl==tr)
		{
			seg[v]=A[tl];
			return;
		}
		int tm=(tl+tr)/2;
		build(v*2,tl,tm,A);
		build(v*2+1,tm+1,tr,A);
		seg[v]=GCD(seg[v*2],seg[v*2+1]);
	}
	static long ask(int v,int tl,int tr,int l,int r)
	{
		if(tl==l && tr==r)return seg[v];
		int tm=(tl+tr)/2;
		if(r<=tm)
		{
			return ask(v*2,tl,tm,l,r);
		}
		else if(l>tm)
		{
			return ask(v*2+1,tm+1,tr,l,r);
		}
		else
		{
			return GCD(ask(v*2,tl,tm,l,tm),ask(v*2+1,tm+1,tr,tm+1,r));
		}
	}

	static int bin(int x,ArrayList<Integer> A)
	{
		int l=0,r=A.size()-1;
		while(l<=r)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a==x)return m;
			if(a<x)l=m+1;
			else r=m-1;
		}
		return 0;
	}
	static int left(int x,ArrayList<Integer> A)
	{
		int l=-1,r=A.size();
		while(r-l>1)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a<=x)l=m;
			else r=m;
		}
		return l;
	}
	static int right(int x,ArrayList<Integer> A)
	{
		int l=-1,r=A.size();
		while(r-l>1)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a<x)l=m;
			else r=m;
		}
		return r;
	}



	static boolean equal(long A[],long B[])
	{
		for(int i=0; i<A.length; i++)if(A[i]!=B[i])return false;
		return true;	
	}


	static int max(int a ,int b,int c,int d)
	{
		a=Math.max(a, b);
		c=Math.max(c,d);
		return Math.max(a, c);
	}
	static int min(int a ,int b,int c,int d)
	{
		a=Math.min(a, b);
		c=Math.min(c,d);
		return Math.min(a, c);
	}



	static HashMap<Integer,Integer> Hash(int A[])
	{
		HashMap<Integer,Integer> mp=new HashMap<>();
		for(int a:A)
		{
			int f=mp.getOrDefault(a,0)+1;
			mp.put(a, f);
		}
		return mp;
	}
	static long mul(long a, long b)
	{
		return ( a %mod * 1L * b%mod )%mod;
	}
	static void swap(int A[],int a,int b)
	{
		int t=A[a];
		A[a]=A[b];
		A[b]=t;
	}


	static int find(int a)
	{
		if(par[a]<0)return a;
		return par[a]=find(par[a]);
	}
	static void union(int a,int b)
	{
		a=find(a);
		b=find(b);
		if(a!=b)
		{
			par[a]+=par[b];
			par[b]=a;
		}
	}
	static boolean isSorted(int A[])
	{
		for(int i=1; i<A.length; i++)
		{
			if(A[i]<A[i-1])return false;
		}
		return true;
	}

	static boolean isDivisible(StringBuilder X,int i,long num)
	{
		long r=0;
		for(; i<X.length(); i++)
		{
			r=r*10+(X.charAt(i)-'0');
			r=r%num;
		}
		return r==0;
	}    



	static int lower_Bound(int A[],int low,int high, int x) 
	{ 
		if (low > high) 
			if (x >= A[high]) 
				return A[high]; 

		int mid = (low + high) / 2; 

		if (A[mid] == x) 
			return A[mid]; 

		if (mid > 0 && A[mid - 1] <= x && x < A[mid]) 
			return A[mid - 1]; 

		if (x < A[mid]) 
			return lower_Bound( A, low, mid - 1, x); 

		return lower_Bound(A, mid + 1, high, x); 
	} 

	static String f(String A)
	{
		String X="";
		for(int i=A.length()-1; i>=0; i--)
		{
			int c=A.charAt(i)-'0';
			X+=(c+1)%2;
		}
		return X;
	}

	static void sort(long[] a) //check for long
	{
		ArrayList<Long> l=new ArrayList<>();
		for (long i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}

	static String swap(String X,int i,int j)
	{
		char ch[]=X.toCharArray();
		char a=ch[i];
		ch[i]=ch[j];
		ch[j]=a;
		return new String(ch);
	}

	static int sD(long n)  
	{  

		if (n % 2 == 0 )  
			return 2;  

		for (int i = 3; i * i <= n; i += 2) {  
			if (n % i == 0 )  
				return i;  
		}  

		return (int)n;  
	}  

	static void setGraph(int N)
	{
		tot=new int[N+1];
		partial=new int[N+1];
		D=new int[N+1];
		P=new int[N+1][(int)(Math.log(N)+10)];
		set=new boolean[N+1];
		g=new ArrayList<ArrayList<edge>>();
		for(int i=0; i<=N; i++)
		{

			g.add(new ArrayList<>());		
			D[i]=0;
			//D2[i]=INF;
		}
	}



	static  long pow(long a,long b)
	{
		//long mod=1000000007;
		long pow=1;
		long x=a;
		while(b!=0)
		{
			if((b&1)!=0)pow=(pow*x)%mod;
			x=(x*x)%mod;
			b/=2;
		}
		return pow;
	}

	static long toggleBits(long x)//one's complement || Toggle bits
	{
		int n=(int)(Math.floor(Math.log(x)/Math.log(2)))+1;

		return ((1<<n)-1)^x;
	}

	static int countBits(long a)
	{
		return (int)(Math.log(a)/Math.log(2)+1);
	}

	static long fact(long N)
	{ 
		long n=2; 
		if(N<=1)return 1;
		else
		{
			for(int i=3; i<=N; i++)n=(n*i)%mod;
		}
		return n;
	}

	static int kadane(int A[])
	{
		int lsum=A[0],gsum=A[0];
		for(int i=1; i<A.length; i++)
		{
			lsum=Math.max(lsum+A[i],A[i]);
			gsum=Math.max(gsum,lsum);
		}
		return gsum;
	}

	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}

	static boolean isPrime(long N)
	{
		if (N<=1)  return false; 
		if (N<=3)  return true; 
		if (N%2 == 0 || N%3 == 0) return false; 
		for (int i=5; i*i<=N; i=i+6) 
			if (N%i == 0 || N%(i+2) == 0) 
				return false; 
		return true; 
	}
	static void print(char A[])
	{
		for(char c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(boolean A[])
	{
		for(boolean c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(int A[])
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();	
	}
	static void print(long A[])
	{
		for(long i:A)System.out.print(i+ " ");
		System.out.println();

	}
	static void print(ArrayList<Integer> A)
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();
	}

	static int i()
	{
		return in.nextInt();
	}

	static long l()
	{
		return in.nextLong();
	}

	static int[] input(int N){
		int A[]=new int[N];
		for(int i=0; i<N; i++)
		{
			A[i]=in.nextInt();
		}
		return A;
	}

	static long[] inputLong(int N)     {
		long A[]=new long[N];
		for(int i=0; i<A.length; i++)A[i]=in.nextLong();
		return A;
	}

	static long GCD(long a,long b) 
	{
		if(b==0)
		{
			return a;
		}
		else return GCD(b,a%b );
	}

}
class edge //implements Comparable<edge>
{
	int a,road;
	edge(int s,int max)
	{
		this.a=s;
		this.road=max;
	}
	//	public int compareTo(edge x)
	//	{
	//		return this.d-x.d;
	//	}
}


//Code For FastReader
//Code For FastReader
//Code For FastReader
//Code For FastReader
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;
	}

}