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.OutputStreamWriter;
import java.io.BufferedWriter;
import java.util.Comparator;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.io.IOException;
import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.math.BigInteger;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 * @author Stanislav Pak
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        TaskD solver = new TaskD();
        solver.solve(1, in, out);
        out.close();
    }
}

class TaskD {
    private static final int UNDEFINED = -1;

    class MyEdge {
        int u;
        int v;
        long w;
        MyEdge(int u, int v, long w) {
            this.u = u;
            this.v = v;
            this.w = w;
        }
    }
    int[] parent;
    long[] a0;
    long[] a1;
    long[] c;
    long[] s;
    public void solve(int testNumber, InputReader in, OutputWriter out) {
        int n = in.readInt();
        parent = ArrayUtils.createArray(n, UNDEFINED);
        a0 = ArrayUtils.createArray(n, 0L);
        a1 = ArrayUtils.createArray(n, 0L);
        c = ArrayUtils.createArray(n, 0L);
        s = ArrayUtils.createArray(n, 0L);
        MyEdge[] edges = new MyEdge[n - 1];
        Graph g = new BidirectionalGraph(n, n - 1);
        for (int i = 0; i < n - 1; ++i) {
            int u = in.readInt() - 1;
            int v = in.readInt() - 1;
            long w = in.readInt();
            edges[i] = new MyEdge(u, v, w);
            g.addWeightedEdge(u, v, w);
        }
        dfs(0, UNDEFINED, g);
        long sumLength = s[0];
        int q = in.readInt();
        for (int i = 0; i < q; ++i) {
            int ei = in.readInt() - 1;
            long w = in.readInt();
            long add = edges[ei].w - w;
            edges[ei].w = w;
            if (parent[edges[ei].u] == edges[ei].v) {
                add *= c[edges[ei].u] * (n - c[edges[ei].u]);
            } else {
                add *= c[edges[ei].v] * (n - c[edges[ei].v]);
            }
            sumLength -= add;
            double ans = sumLength * 6.0 / n / (n - 1);
            out.printLine(ans);
        }
    }

    private void dfs(int v, int p, Graph g) {
        c[v] = 0;
        parent[v] = p;
        long sa1 = 0;
        long sca1 = 0;
        long scw = 0;
        long sccw = 0;
        for (Edge e : g.outbound(v)) {
            int u =  e.getDestination();
            if (u != p) {
                dfs(u, v, g);
                c[v] += c[u];
                a1[v] += a1[u] + e.getWeight() * c[u];
                sa1 += a1[u];
                sca1 += c[u] * a1[u];
                scw += c[u] * e.getWeight();
                sccw += c[u] * c[u] * e.getWeight();
                s[v] += s[u];
            }
        }
        a0[v] = c[v] * sa1 - sca1;
        a0[v] += c[v] * scw - sccw;
        c[v] += 1;
        s[v] += a0[v] + a1[v];
    }
}

class InputReader {

    private InputStream stream;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
    private SpaceCharFilter filter;

    public InputReader(InputStream stream) {
        this.stream = stream;
    }

    public int read() {
        if (numChars == -1)
            throw new InputMismatchException();
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }

    public int readInt() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9')
                throw new InputMismatchException();
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }

    public boolean isSpaceChar(int c) {
        if (filter != null)
            return filter.isSpaceChar(c);
        return isWhitespace(c);
    }

    public static boolean isWhitespace(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    public interface SpaceCharFilter {
        public boolean isSpaceChar(int ch);
    }
}

class OutputWriter {
    private final PrintWriter writer;

    public OutputWriter(OutputStream outputStream) {
        writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
    }

    public void print(Object...objects) {
        for (int i = 0; i < objects.length; i++) {
            if (i != 0)
                writer.print(' ');
            writer.print(objects[i]);
        }
    }

    public void printLine(Object...objects) {
        print(objects);
        writer.println();
    }

    public void close() {
        writer.close();
    }

}

class ArrayUtils {

    public static int[] createArray(int count, int value) {
        int[] array = new int[count];
        Arrays.fill(array, value);
        return array;
    }

    public static long[] createArray(int count, long value) {
        long[] array = new long[count];
        Arrays.fill(array, value);
        return array;
    }

}

class Graph {
    public static final int REMOVED_BIT = 0;

    protected int vertexCount;
    protected int edgeCount;

    private int[] firstOutbound;
    private int[] firstInbound;

    private Edge[] edges;
    private int[] nextInbound;
    private int[] nextOutbound;
    private int[] from;
    private int[] to;
    private long[] weight;
    public long[] capacity;
    private int[] reverseEdge;
    private int[] flags;

    public Graph(int vertexCount, int edgeCapacity) {
        this.vertexCount = vertexCount;
        firstOutbound = new int[vertexCount];
        Arrays.fill(firstOutbound, -1);

        from = new int[edgeCapacity];
        to = new int[edgeCapacity];
        nextOutbound = new int[edgeCapacity];
        flags = new int[edgeCapacity];
    }

    public int addEdge(int fromID, int toID, long weight, long capacity, int reverseEdge) {
        ensureEdgeCapacity(edgeCount + 1);
        if (firstOutbound[fromID] != -1)
            nextOutbound[edgeCount] = firstOutbound[fromID];
        else
            nextOutbound[edgeCount] = -1;
        firstOutbound[fromID] = edgeCount;
        if (firstInbound != null) {
            if (firstInbound[toID] != -1)
                nextInbound[edgeCount] = firstInbound[toID];
            else
                nextInbound[edgeCount] = -1;
            firstInbound[toID] = edgeCount;
        }
        this.from[edgeCount] = fromID;
        this.to[edgeCount] = toID;
        if (capacity != 0) {
            if (this.capacity == null)
                this.capacity = new long[from.length];
            this.capacity[edgeCount] = capacity;
        }
        if (weight != 0) {
            if (this.weight == null)
                this.weight = new long[from.length];
            this.weight[edgeCount] = weight;
        }
        if (reverseEdge != -1) {
            if (this.reverseEdge == null) {
                this.reverseEdge = new int[from.length];
                Arrays.fill(this.reverseEdge, 0, edgeCount, -1);
            }
            this.reverseEdge[edgeCount] = reverseEdge;
        }
        if (edges != null)
            edges[edgeCount] = createEdge(edgeCount);
        return edgeCount++;
    }

    protected final GraphEdge createEdge(int id) {
        return new GraphEdge(id);
    }

    public final int addFlowWeightedEdge(int from, int to, long weight, long capacity) {
        if (capacity == 0) {
            return addEdge(from, to, weight, 0, -1);
        } else {
            int lastEdgeCount = edgeCount;
            addEdge(to, from, -weight, 0, lastEdgeCount + entriesPerEdge());
            return addEdge(from, to, weight, capacity, lastEdgeCount);
        }
    }

    protected int entriesPerEdge() {
        return 1;
    }

    public final int addWeightedEdge(int from, int to, long weight) {
        return addFlowWeightedEdge(from, to, weight, 0);
    }

    protected final int edgeCapacity() {
        return from.length;
    }

    public final int destination(int id) {
        return to[id];
    }

    public final long weight(int id) {
        if (weight == null)
            return 0;
        return weight[id];
    }

    protected final void initEdges() {
        if (edges == null) {
            edges = new Edge[from.length];
            for (int i = 0; i < edgeCount; i++)
                edges[i] = createEdge(i);
        }
    }

    public final boolean flag(int id, int bit) {
        return (flags[id] >> bit & 1) != 0;
    }

    public final void setFlag(int id, int bit) {
        flags[id] |= 1 << bit;
    }

    public final void removeEdge(int id) {
        setFlag(id, REMOVED_BIT);
    }

    public final boolean isRemoved(int id) {
        return flag(id, REMOVED_BIT);
    }

    public final Iterable<Edge> outbound(final int id) {
        initEdges();
        return new Iterable<Edge>() {
            public Iterator<Edge> iterator() {
                return new EdgeIterator(id, firstOutbound, nextOutbound);
            }
        };
    }

    protected void ensureEdgeCapacity(int size) {
        if (from.length < size) {
            int newSize = Math.max(size, 2 * from.length);
            if (edges != null)
                edges = resize(edges, newSize);
            from = resize(from, newSize);
            to = resize(to, newSize);
            nextOutbound = resize(nextOutbound, newSize);
            if (nextInbound != null)
                nextInbound = resize(nextInbound, newSize);
            if (weight != null)
                weight = resize(weight, newSize);
            if (capacity != null)
                capacity = resize(capacity, newSize);
            if (reverseEdge != null)
                reverseEdge = resize(reverseEdge, newSize);
            flags = resize(flags, newSize);
        }
    }

    protected final int[] resize(int[] array, int size) {
        int[] newArray = new int[size];
        System.arraycopy(array, 0, newArray, 0, array.length);
        return newArray;
    }

    private long[] resize(long[] array, int size) {
        long[] newArray = new long[size];
        System.arraycopy(array, 0, newArray, 0, array.length);
        return newArray;
    }

    private Edge[] resize(Edge[] array, int size) {
        Edge[] newArray = new Edge[size];
        System.arraycopy(array, 0, newArray, 0, array.length);
        return newArray;
    }

    protected class GraphEdge implements Edge {
        protected int id;

        protected GraphEdge(int id) {
            this.id = id;
        }

        public int getDestination() {
            return destination(id);
        }

        public long getWeight() {
            return weight(id);
        }

    }

    public class EdgeIterator implements Iterator<Edge> {
        private int edgeID;
        private final int[] next;
        private int lastID = -1;

        public EdgeIterator(int id, int[] first, int[] next) {
            this.next = next;
            edgeID = nextEdge(first[id]);
        }

        private int nextEdge(int id) {
            while (id != -1 && isRemoved(id))
                id = next[id];
            return id;
        }

        public boolean hasNext() {
            return edgeID != -1;
        }

        public Edge next() {
            if (edgeID == -1)
                throw new NoSuchElementException();
            lastID = edgeID;
            edgeID = nextEdge(next[lastID]);
            return edges[lastID];
        }

        public void remove() {
            if (lastID == -1)
                throw new IllegalStateException();
            removeEdge(lastID);
            lastID = -1;
        }
    }

}

class BidirectionalGraph extends Graph {
    public int[] transposedEdge;

    public BidirectionalGraph(int vertexCount, int edgeCapacity) {
        super(vertexCount, 2 * edgeCapacity);
        transposedEdge = new int[2 * edgeCapacity];
    }

    public int addEdge(int fromID, int toID, long weight, long capacity, int reverseEdge) {
        int lastEdgeCount = edgeCount;
        super.addEdge(fromID, toID, weight, capacity, reverseEdge);
        super.addEdge(toID, fromID, weight, capacity, reverseEdge == -1 ? -1 : reverseEdge + 1);
        this.transposedEdge[lastEdgeCount] = lastEdgeCount + 1;
        this.transposedEdge[lastEdgeCount + 1] = lastEdgeCount;
        return lastEdgeCount;
    }

    protected int entriesPerEdge() {
        return 2;
    }

    protected void ensureEdgeCapacity(int size) {
        if (size > edgeCapacity()) {
            super.ensureEdgeCapacity(size);
            transposedEdge = resize(transposedEdge, edgeCapacity());
        }
    }
}

interface Edge {
    public int getDestination();
    public long getWeight();
}