Problem: New Year is coming in Tree World! In this world, as the name implies, there are n cities connected by n - 1 roads, and for any two distinct cities there always exists a path between them. The cities are numbered by integers from 1 to n, and the roads are numbered by integers from 1 to n - 1. Let's define d(u, v) as total length of roads on the path between city u and city v.

As an annual event, people in Tree World repairs exactly one road per year. As a result, the length of one road decreases. It is already known that in the i-th year, the length of the ri-th road is going to become wi, which is shorter than its length before. Assume that the current year is year 1.

Three Santas are planning to give presents annually to all the children in Tree World. In order to do that, they need some preparation, so they are going to choose three distinct cities c1, c2, c3 and make exactly one warehouse in each city. The k-th (1 ≤ k ≤ 3) Santa will take charge of the warehouse in city ck.

It is really boring for the three Santas to keep a warehouse alone. So, they decided to build an only-for-Santa network! The cost needed to build this network equals to d(c1, c2) + d(c2, c3) + d(c3, c1) dollars. Santas are too busy to find the best place, so they decided to choose c1, c2, c3 randomly uniformly over all triples of distinct numbers from 1 to n. Santas would like to know the expected value of the cost needed to build the network.

However, as mentioned, each year, the length of exactly one road decreases. So, the Santas want to calculate the expected after each length change. Help them to calculate the value.

Input

The first line contains an integer n (3 ≤ n ≤ 105) — the number of cities in Tree World.

Next n - 1 lines describe the roads. The i-th line of them (1 ≤ i ≤ n - 1) contains three space-separated integers ai, bi, li (1 ≤ ai, bi ≤ n, ai ≠ bi, 1 ≤ li ≤ 103), denoting that the i-th road connects cities ai and bi, and the length of i-th road is li.

The next line contains an integer q (1 ≤ q ≤ 105) — the number of road length changes.

Next q lines describe the length changes. The j-th line of them (1 ≤ j ≤ q) contains two space-separated integers rj, wj (1 ≤ rj ≤ n - 1, 1 ≤ wj ≤ 103). It means that in the j-th repair, the length of the rj-th road becomes wj. It is guaranteed that wj is smaller than the current length of the rj-th road. The same road can be repaired several times.

Output

Output q numbers. For each given change, print a line containing the expected cost needed to build the network in Tree World. The answer will be considered correct if its absolute and relative error doesn't exceed 10 - 6.

Examples

Input

3
2 3 5
1 3 3
5
1 4
2 2
1 2
2 1
1 1


Output

14.0000000000
12.0000000000
8.0000000000
6.0000000000
4.0000000000


Input

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


Output

19.6000000000
18.6000000000
16.6000000000
13.6000000000
12.6000000000

Note

Consider the first sample. There are 6 triples: (1, 2, 3), (1, 3, 2), (2, 1, 3), (2, 3, 1), (3, 1, 2), (3, 2, 1). Because n = 3, the cost needed to build the network is always d(1, 2) + d(2, 3) + d(3, 1) for all the triples. So, the expected cost equals to d(1, 2) + d(2, 3) + d(3, 1).

Solution (in JAVA):

Solution:
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.io.DataInputStream;
import java.io.FileInputStream;

public class NewYearSantaNetwork_codeforces {

	public static void main(String[] args) throws IOException {
		Reader in = new Reader();
		PrintWriter out = new PrintWriter(System.out,true);
		double en = in.nextDouble();
		int n =(int)en;
		long[][] E = new long[n][4];
		for(int i =1;i<n;i++){
			E[i][0]=in.nextInt();
			E[i][1]=in.nextInt();
			E[i][2]=in.nextInt();
		}
		ArrayList<GraphNode> tree = new ArrayList<GraphNode>(n+1);
		GraphNode root,temp;
		for(int i = 0;i<=n;i++){
			tree.add(new GraphNode(i));
		}
		for(int i = 1;i<n;i++){
			root=tree.get((int)E[i][0]);
			temp=tree.get((int)E[i][1]);
			root.adjacent.add(temp);
			temp.adjacent.add(root);
		}
		root = tree.get(1);//weight
		//Graph.print(Graph.BFS(tree, root));
		root.discoveryTime = 1;//depth
		DFS(tree,root);
//		int n1,n2;
		double sum=0;
		GraphNode temp1;
		for(int i = 1;i<n;i++){
			temp1=tree.get((int)E[i][0]);
			temp=tree.get((int)E[i][1]);
			if(temp1.discoveryTime>temp.discoveryTime){
				//E[i][3]=E[i][2]*(root.data*temp.discoveryTime);
				E[i][3]=E[i][2]*((long)temp1.data*(root.data-temp1.data));
			}
			else{
				E[i][3]=E[i][2]*((long)temp.data*(root.data-temp.data));
			}
			sum+=E[i][3];
			//System.out.println("SUM ="+sum+" lsfn = "+E[i][3]);
		}
		double p = 6/(en*(en-1));
		//sum*=p;
		//System.out.println("initial cost = "+sum*p);
		//lets answer queries now!
		int r,w,q = in.nextInt();
		long nVal,diff;
		for(int i = 0;i<q;i++){
		//	out.println("Waiting for input ...");
			r = in.nextInt();
			w = in.nextInt();
			E[r][2] = w;
			temp1=tree.get((int)E[r][0]);//u
			temp=tree.get((int)E[r][1]);//v
			if(temp1.discoveryTime>temp.discoveryTime){
				nVal=E[r][2]*((long)temp1.data*(root.data-temp1.data));
			}
			else{
				nVal=E[r][2]*((long)temp.data*(root.data-temp.data));
			}
			diff = nVal - E[r][3];
			E[r][3] = nVal;
			sum+=diff;
			out.println(sum*p);
		}
	}

	private static int DFS(ArrayList<GraphNode> tree, GraphNode root) {
		if(root ==null) return 0;
		//System.out.println("DFS called with root"+root);
		int weight = 1;
		root.color = 'g';
		
		for(GraphNode v:root.adjacent){
			if(v.color!='w')continue;
			v.discoveryTime=root.discoveryTime+1;
			weight+=DFS(tree,v);
		}
		root.data = weight;
		root.color='b';
		return weight;
	}
	
}
class GraphNode implements Comparable<GraphNode>{
	int data;
	int color;
	int discoveryTime,finishTime;
	GraphNode pre;
	ArrayList<GraphNode> adjacent ;//references to adjacent graph nodes
	//@SuppressWarnings("rawtypes")
	//ArrayList extraParameters;
	public GraphNode(int d,ArrayList<GraphNode> a){
		data = d;
		adjacent = a;
		color='w';
		discoveryTime = finishTime = -1;
		pre = null;
		//extraParameters = new ArrayList();
	}
	public GraphNode(ArrayList<GraphNode> a){
		this(-1,a);
	}
	public GraphNode(int d){
		this(d,new ArrayList<GraphNode>());
	}
	public GraphNode(){
		this(-1);
	}
	public String toString(){
		String str = "";
		str+="{"+data+",["+discoveryTime+"/"+finishTime+"]"+"} ";
		//str+="{"+data+","+color+"} ";
		return str;
	}
	public int compareTo(GraphNode x) {
		// http://tutorials.jenkov.com/java-collections/sorting.html
		if(data==x.data)return 0;
		else if(data<x.data) return -1;
		else return 1;
	}
}

class Reader {
    final private int BUFFER_SIZE = 1 << 16;private DataInputStream din;private byte[] buffer;private int bufferPointer, bytesRead;
    public Reader(){din=new DataInputStream(System.in);buffer=new byte[BUFFER_SIZE];bufferPointer=bytesRead=0;}
    public Reader(String file_name) throws IOException{din=new DataInputStream(new FileInputStream(file_name));buffer=new byte[BUFFER_SIZE];bufferPointer=bytesRead=0;}
    public String readLine() throws IOException{byte[] buf=new byte[64];int cnt=0,c;while((c=read())!=-1){if(c=='\n')break;buf[cnt++]=(byte)c;}return new String(buf,0,cnt);}
    public int nextInt() throws IOException{int ret=0;byte c=read();while(c<=' ')c=read();boolean neg=(c=='-');if(neg)c=read();do{ret=ret*10+c-'0';}while((c=read())>='0'&&c<='9');if(neg)return -ret;return ret;} 
    public long nextLong() throws IOException{long ret=0;byte c=read();while(c<=' ')c=read();boolean neg=(c=='-');if(neg)c=read();do{ret=ret*10+c-'0';}while((c=read())>='0'&&c<='9');if(neg)return -ret;return ret;}
    public double nextDouble() throws IOException{double ret=0,div=1;byte c=read();while(c<=' ')c=read();boolean neg=(c=='-');if(neg)c = read();do {ret=ret*10+c-'0';}while((c=read())>='0'&&c<='9');
        if(c=='.')while((c=read())>='0'&&c<='9')ret+=(c-'0')/(div*=10);if(neg)return -ret;return ret;}
    private void fillBuffer() throws IOException{bytesRead=din.read(buffer,bufferPointer=0,BUFFER_SIZE);if(bytesRead==-1)buffer[0]=-1;}
    private byte read() throws IOException{if(bufferPointer==bytesRead)fillBuffer();return buffer[bufferPointer++];}
    public void close() throws IOException{if(din==null) return;din.close();}
}