A system of n vessels with water is given. Several pairs of vessels are connected by tubes with transfusion mechanisms. One may transfer an integer amount of liters of water between two vessels connected by such tube (tube works in both directions). There might be multiple tubes between two vessels. Total number of tubes equals e. Volume of each vessel equals v liters. Of course, the amount of the water in any vessel cannot exceed v liters in the process of transfusions.

Given the initial amounts ai of water in the vessels and the desired amounts bi find a sequence of transfusions that deals with the task. Total number of transfusions must not exceed 2·n2.

Input

First line of the input contains integers n, v, e (1 ≤ n ≤ 300, 1 ≤ v ≤ 109, 0 ≤ e ≤ 50000).

Next two lines contain n integers each: initial ai and the desired amounts bi of water in corresponding vessels (0 ≤ ai, bi ≤ v).

Next e lines describe one tube each in the format x y (1 ≤ x, y ≤ n, x ≠ y) for a tube between vessels number x and y. There might be multiple tubes between two vessels. You may assume that vessels are numbered from 1 to n in some way.

Output

Print "NO" (without quotes), if such sequence of transfusions does not exist.

Otherwise print any suitable sequence in the following format. On the first line print the total number of transfusions k (k should not exceed 2·n2). In the following k lines print transfusions in the format x y d (transfusion of d liters from the vessel number x to the vessel number y, x and y must be distinct). For all transfusions d must be a non-negative integer.

Examples

Input

2 10 1
1 9
5 5
1 2


Output

1
2 1 4


Input

2 10 0
5 2
4 2


Output

NO


Input

2 10 0
4 2
4 2


Output

0
import java.util.List;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Comparator;
import java.io.BufferedReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.util.Collections;
import java.io.InputStream;

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

class TaskE {

    private int vertexCounter, edgeCounter, value;
    private int[] path;
    private long[] initial, desired;
    private List<Integer>[] graph;
    private DSU dsu;
    private List<Integer> more, less;
    private boolean[] ready;
    private List<Transfusion> answer;

    public void solve(int testNumber, InputReader in, PrintWriter out) {

        vertexCounter = in.nextInt();
        value = in.nextInt();
        edgeCounter = in.nextInt();

        initial = new long[vertexCounter];
        desired = new long[vertexCounter];
        ready = new boolean[vertexCounter];
        more = new ArrayList<Integer>();
        less = new ArrayList<Integer>();
        answer = new ArrayList<Transfusion>();
        graph = new ArrayList[vertexCounter];
        for (int i = 0; i < vertexCounter; ++i)
            graph[i] = new ArrayList<Integer>();

        for (int i = 0; i < vertexCounter; ++i)
            initial[i] = in.nextInt();
        for (int i = 0; i < vertexCounter; ++i)
            desired[i] = in.nextInt();

        dsu = new DSU(vertexCounter, initial, desired);

        int v, u;
        for (int i = 0; i < edgeCounter; ++i) {
            v = in.nextInt() - 1;
            u = in.nextInt() - 1;
            graph[u].add(v);
            graph[v].add(u);
            dsu.union(v, u);
        }

        if (!dsu.check()) {
            out.println("NO");
            return;
        }

        for (int i = 0; i < vertexCounter; ++i)
            if (initial[i] == desired[i])
                ready[i] = true;
            else if (initial[i] > desired[i])
                more.add(i);
            else
                less.add(i);

        Comparator<Integer> cmp = new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return Integer.compare(dsu.getSet(o1), dsu.getSet(o2));
            }
        };
        Collections.sort(more, cmp);
        Collections.sort(less, cmp);

        int current = 0;
        for (int i = 0; i < more.size(); ++i)
            if (initial[more.get(i)] - desired[more.get(i)] > desired[less.get(current)] - initial[less.get(current)]) {
                transfusion(more.get(i), less.get(current), (int) (desired[less.get(current)] - initial[less.get(current)]));
                ready[less.get(current)] = true;
                current++;
                i--;
            } else if (initial[more.get(i)] - desired[more.get(i)] < desired[less.get(current)] - initial[less.get(current)]) {
                transfusion(more.get(i), less.get(current), (int) (initial[more.get(i)] - desired[more.get(i)]));
                ready[more.get(i)] = true;
            } else {
                transfusion(more.get(i), less.get(current), (int) (initial[more.get(i)] - desired[more.get(i)]));
                ready[more.get(i)] = true;
                ready[less.get(current)] = true;
                current++;
            }

        out.println(answer.size());
        for (Transfusion transfusion : answer)
            transfusion.println(out);
    }

    private void transfusion(int from, int to, int delta) {
        path = new int[vertexCounter];
        Arrays.fill(path, -1);
        bfs(to, from);
        flow(from, to, delta);
    }

    private void bfs(int start, int finish) {
        int[] queue = new int[vertexCounter];
        int size = 0;
        int next = 0;
        queue[size++] = start;
        while (next < size) {
            int v = queue[next++];
            for (int u : graph[v])
                if (path[u] == -1) {
                    path[u] = v;
                    if (u == finish)
                        return;
                    queue[size++] = u;
                }
        }
    }

    private void flow(int from, int to, int delta) {
        if (from == to)
            return;
       
        if (initial[path[from]] + delta <= value) {

                initial[from] -= delta;
                initial[path[from]] += delta;
            answer.add(new Transfusion(from, path[from], delta));

            flow(path[from], to, delta);
        } else if (initial[path[from]] >= delta) {
            flow(path[from], to, delta);

                initial[from] -= delta;
                initial[path[from]] += delta;
            answer.add(new Transfusion(from, path[from], delta));
        } else {
            int difference = (int) (delta - initial[path[from]]);

                initial[from] -= difference;
                initial[path[from]] += difference;
            answer.add(new Transfusion(from, path[from], difference));

            flow(path[from], to, delta);

                initial[from] -= delta - difference;
                initial[path[from]] += delta - difference;
            answer.add(new Transfusion(from, path[from], delta - difference));
        }
    }

}

class DSU {

    public int[] parent, rank;
    private long[] initial, desired;

    public DSU (int size, long[] initial, long[] desired) {
        parent = new int[size];
        rank = new int[size];
        this.initial = Arrays.copyOf(initial, initial.length);
        this.desired = Arrays.copyOf(desired, desired.length);
        for (int i = 0; i < size; ++i)
            parent[i] = i;
        for (int i = 0; i < size; ++i) {
            this.initial[getSet(i)] += initial[i];
            this.desired[getSet(i)] += desired[i];
        }
    }

    public int getSet(int v) {
        if (parent[v] == v)
            return v;
        return parent[v] = getSet(parent[v]);
    }

    public void union(int v, int u) {
        int a = getSet(v);
        int b = getSet(u);
        if (a != b) {
            if (rank[a] < rank[b]) {
                a ^= b;
                b ^= a;
                a ^= b;
            }
            parent[b] = a;
            if (rank[a] == rank[b])
                ++rank[a];
        }
    }

    public boolean check() {
        for (int v = 0; v < initial.length; ++v) {
            int p = getSet(v);
            if (p != v) {
                initial[p] += initial[v];
                desired[p] += desired[v];
                initial[v] = 0;
                desired[v] = 0;
            }
        }
        for (int i = 0; i < initial.length; ++i)
            if (initial[i] != desired[i])
                return false;
        return true;
    }

}

class Transfusion {

    public int from, to, value;

    public Transfusion(int x, int y, int v) {
        from = x;
        to = y;
        value = v;
    }

    public void println(PrintWriter out) {
        out.print(from + 1);
        out.print(" ");
        out.print(to + 1);
        out.print(" ");
        out.println(value);
    }

}

class InputReader {

    private static BufferedReader bufferedReader;
    private static StringTokenizer stringTokenizer;

    public InputReader(InputStream inputStream) {
        bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
        stringTokenizer = null;
    }

    public String next() {
        while(stringTokenizer == null || !stringTokenizer.hasMoreTokens()) {
            try {
                stringTokenizer = new StringTokenizer(bufferedReader.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return stringTokenizer.nextToken();
    }

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

    }

