Problem: ALT is a planet in a galaxy called "Encore". Humans rule this planet but for some reason there's no dog in their planet, so the people there are sad and depressed. Rick and Morty are universal philanthropists and they want to make people in ALT happy. 

ALT has n cities numbered from 1 to n and n - 1 bidirectional roads numbered from 1 to n - 1. One can go from any city to any other city using these roads.

There are two types of people in ALT:

  1. Guardians. A guardian lives in a house alongside a road and guards the road. 
  2. Citizens. A citizen lives in a house inside a city and works in an office in another city. 



Every person on ALT is either a guardian or a citizen and there's exactly one guardian alongside each road. 

<image>

Rick and Morty talked to all the people in ALT, and here's what they got:

  * There are m citizens living in ALT. 
  * Citizen number i lives in city number xi and works in city number yi. 
  * Every day each citizen will go through all roads along the shortest path from his home to his work. 
  * A citizen will be happy if and only if either he himself has a puppy himself or all of guardians along his path to his work has a puppy (he sees the guardian's puppy in each road and will be happy). 
  * A guardian is always happy. 



You need to tell Rick and Morty the minimum number of puppies they need in order to make all people in ALT happy, and also provide an optimal way to distribute these puppies.

Input

The first line of input contains two integers n and m (2 ≤ n ≤ 2 × 104, 1 ≤ m ≤ 104) — number of cities and number of citizens respectively.

The next n - 1 lines contain the roads, i-th line contains endpoint of i-th edge, v and u (1 ≤ v, u ≤ n, v ≠ u).

The next m lines contain the information about citizens. i-th line contains two integers xi and yi (1 ≤ xi, yi ≤ n, xi ≠ yi).

Output

In the first line of input print a single integer k, the total number of puppies they need (1 ≤ k ≤ n).

In the second line print an integer q, the number of puppies to give to citizens, followed by q distinct integers a1, a2, ..., aq, index of citizens to give puppy to (0 ≤ q ≤ min(m, k), 1 ≤ ai ≤ m).

In the third line print an integer e, the number of puppies to give to guardians, followed by e distinct integers b1, b2, ..., be, index of road of guardians to give puppy to (0 ≤ e ≤ min(n - 1, k), 1 ≤ bi ≤ n - 1).

Sum of q and e should be equal to k.

Examples

Input

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


Output

3
1 5 
2 3 1 


Input

4 7
3 4
1 4
2 1
4 2
4 2
2 4
1 4
2 1
3 1
4 2


Output

3
1 6 
2 2 3 

Note

Map of ALT in the first sample testcase (numbers written on a road is its index):

<image>

Map of ALT in the second sample testcase (numbers written on a road is its index): 

<image>

Solution (in JAVA):

Solution:
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Deque;
import java.util.ArrayList;
import java.util.Map;
import java.io.OutputStreamWriter;
import java.io.OutputStream;
import java.util.Collection;
import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.List;
import java.io.Closeable;
import java.io.Writer;
import java.util.ArrayDeque;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) throws Exception {
        Thread thread = new Thread(null, new TaskAdapter(), "", 1 << 27);
        thread.start();
        thread.join();
    }

    static class TaskAdapter implements Runnable {
        @Override
        public void run() {
            InputStream inputStream = System.in;
            OutputStream outputStream = System.out;
            FastInput in = new FastInput(inputStream);
            FastOutput out = new FastOutput(outputStream);
            EALT solver = new EALT();
            solver.solve(1, in, out);
            out.close();
        }
    }

    static class EALT {
        int n;
        int m;
        LongMinimumCloseSubGraph subGraph;
        int idAlloc;

        public void solve(int testNumber, FastInput in, FastOutput out) {
            n = in.readInt();
            m = in.readInt();
            idAlloc = m + n - 1;
            Node[] nodes = new Node[n];
            for (int i = 0; i < n; i++) {
                nodes[i] = new Node();
                nodes[i].id = i + 1;
            }

            MultiWayIntegerStack edges = new MultiWayIntegerStack(n, n * 2);
            for (int i = 1; i < n; i++) {
                int aId = in.readInt() - 1;
                int bId = in.readInt() - 1;
                Node a = nodes[aId];
                Node b = nodes[bId];
                Edge e = new Edge();
                e.a = a;
                e.b = b;
                e.id = i - 1;
                a.next.add(e);
                b.next.add(e);

                edges.addLast(aId, bId);
                edges.addLast(bId, aId);
            }

            LcaOnTree lcaOnTree = new LcaOnTree(edges, 0);

            int vertexNum = m + n - 1 + (n - 1) * 15;
            long[] weights = new long[vertexNum];
            for (int i = 0; i < m; i++) {
                weights[idOfCitizen(i)] = 1;
            }
            for (int i = 0; i < n - 1; i++) {
                weights[idOfEdge(i)] = -1;
            }
            subGraph = new LongMinimumCloseSubGraph(weights);
            dfs(nodes[0], null, null, 0);

            for (int i = 0; i < m; i++) {
                int a = in.readInt() - 1;
                int b = in.readInt() - 1;
                int lca = lcaOnTree.lca(a, b);
                findLCA(nodes[a], nodes[lca].depth, i);
                findLCA(nodes[b], nodes[lca].depth, i);
            }

            subGraph.solve();
            IntegerList citizen = new IntegerList(m);
            IntegerList guard = new IntegerList(n);
            boolean[] status = subGraph.getStatus();
            for (int i = 0; i < m; i++) {
                if (!status[i]) {
                    citizen.add(i);
                }
            }
            for (int i = 0; i < n - 1; i++) {
                if (status[m + i]) {
                    guard.add(i);
                }
            }

            out.println(citizen.size() + guard.size());
            out.append(citizen.size()).append(' ');
            for (int i = 0; i < citizen.size(); i++) {
                out.append(citizen.get(i) + 1).append(' ');
            }
            out.println();
            out.append(guard.size()).append(' ');
            for (int i = 0; i < guard.size(); i++) {
                out.append(guard.get(i) + 1).append(' ');
            }
        }

        public int idOfCitizen(int i) {
            return i;
        }

        public int idOfEdge(int i) {
            return m + i;
        }

        public int nextId() {
            return ++idAlloc;
        }

        public void dfs(Node root, Node p, Edge from, int depth) {
            root.depth = depth;
            if (from != null) {
                root.jump[0] = p;
                root.dependencyIds[0] = idOfEdge(from.id);
                for (int i = 0; root.jump[i].jump[i] != null; i++) {
                    root.jump[i + 1] = root.jump[i].jump[i];
                    if (root.jump[i + 1] != null) {
                        root.dependencyIds[i + 1] = nextId();
                        subGraph.addDependency(root.dependencyIds[i + 1], root.dependencyIds[i]);
                        subGraph.addDependency(root.dependencyIds[i + 1], root.jump[i].dependencyIds[i]);
                    }
                }
            }
            for (Edge e : root.next) {
                if (e == from) {
                    continue;
                }
                Node node = e.other(root);
                dfs(node, root, e, depth + 1);
            }
        }

        public void findLCA(Node a, int targetDepth, int citizen) {
            if (a.depth == targetDepth) {
                return;
            }
            int differ = a.depth - targetDepth;
            int log = CachedLog2.floorLog(differ);
            subGraph.addDependency(idOfCitizen(citizen), a.dependencyIds[log]);
            findLCA(a.jump[log], targetDepth, citizen);
        }

    }

    static class IntegerList implements Cloneable {
        private int size;
        private int cap;
        private int[] data;
        private static final int[] EMPTY = new int[0];

        public IntegerList(int cap) {
            this.cap = cap;
            if (cap == 0) {
                data = EMPTY;
            } else {
                data = new int[cap];
            }
        }

        public IntegerList(IntegerList list) {
            this.size = list.size;
            this.cap = list.cap;
            this.data = Arrays.copyOf(list.data, size);
        }

        public IntegerList() {
            this(0);
        }

        public void ensureSpace(int req) {
            if (req > cap) {
                while (cap < req) {
                    cap = Math.max(cap + 10, 2 * cap);
                }
                data = Arrays.copyOf(data, cap);
            }
        }

        private void checkRange(int i) {
            if (i < 0 || i >= size) {
                throw new ArrayIndexOutOfBoundsException("index " + i + " out of range");
            }
        }

        public int get(int i) {
            checkRange(i);
            return data[i];
        }

        public void add(int x) {
            ensureSpace(size + 1);
            data[size++] = x;
        }

        public void addAll(int[] x, int offset, int len) {
            ensureSpace(size + len);
            System.arraycopy(x, offset, data, size, len);
            size += len;
        }

        public void addAll(IntegerList list) {
            addAll(list.data, 0, list.size);
        }

        public int size() {
            return size;
        }

        public int[] toArray() {
            return Arrays.copyOf(data, size);
        }

        public String toString() {
            return Arrays.toString(toArray());
        }

        public boolean equals(Object obj) {
            if (!(obj instanceof IntegerList)) {
                return false;
            }
            IntegerList other = (IntegerList) obj;
            return SequenceUtils.equal(data, 0, size - 1, other.data, 0, other.size - 1);
        }

        public int hashCode() {
            int h = 1;
            for (int i = 0; i < size; i++) {
                h = h * 31 + Integer.hashCode(data[i]);
            }
            return h;
        }

        public IntegerList clone() {
            IntegerList ans = new IntegerList();
            ans.addAll(this);
            return ans;
        }

    }

    static class CachedLog2 {
        private static final int BITS = 16;
        private static final int LIMIT = 1 << BITS;
        private static final byte[] CACHE = new byte[LIMIT];

        static {
            int b = 0;
            for (int i = 0; i < LIMIT; i++) {
                while ((1 << (b + 1)) <= i) {
                    b++;
                }
                CACHE[i] = (byte) b;
            }
        }

        public static int floorLog(int x) {
            return x < LIMIT ? CACHE[x] : (BITS + CACHE[x >>> BITS]);
        }

    }

    static class Node {
        List<Edge> next = new ArrayList<>();
        int depth;
        Node[] jump = new Node[15];
        int[] dependencyIds = new int[15];
        int id;

        public String toString() {
            return "" + id;
        }

    }

    static class FastInput {
        private final InputStream is;
        private byte[] buf = new byte[1 << 13];
        private int bufLen;
        private int bufOffset;
        private int next;

        public FastInput(InputStream is) {
            this.is = is;
        }

        private int read() {
            while (bufLen == bufOffset) {
                bufOffset = 0;
                try {
                    bufLen = is.read(buf);
                } catch (IOException e) {
                    bufLen = -1;
                }
                if (bufLen == -1) {
                    return -1;
                }
            }
            return buf[bufOffset++];
        }

        public void skipBlank() {
            while (next >= 0 && next <= 32) {
                next = read();
            }
        }

        public int readInt() {
            int sign = 1;

            skipBlank();
            if (next == '+' || next == '-') {
                sign = next == '+' ? 1 : -1;
                next = read();
            }

            int val = 0;
            if (sign == 1) {
                while (next >= '0' && next <= '9') {
                    val = val * 10 + next - '0';
                    next = read();
                }
            } else {
                while (next >= '0' && next <= '9') {
                    val = val * 10 - next + '0';
                    next = read();
                }
            }

            return val;
        }

    }

    static class LongMinimumCloseSubGraph {
        private LongISAP isap;
        private int n;
        private long sumOfPositive;
        private boolean solved;
        private long minCut;
        private boolean[] status;

        public LongMinimumCloseSubGraph(long[] weight) {
            this.n = weight.length;
            isap = new LongISAP(n + 2);
            int idOfSrc = n;
            int idOfDst = n + 1;
            isap.setSource(idOfSrc);
            isap.setTarget(idOfDst);

            for (int i = 0; i < n; i++) {
                if (weight[i] > 0) {
                    isap.getChannel(idOfSrc, i).reset(weight[i], 0);
                    sumOfPositive += weight[i];
                }
                if (weight[i] < 0) {
                    isap.getChannel(i, idOfDst).reset(-weight[i], 0);
                }
            }
        }

        public void addDependency(int from, int to) {
            if (!(from >= 0 && from < n && to >= 0 && to < n)) {
                throw new IllegalArgumentException();
            }
            isap.getChannel(from, to).reset((long) 1e18, 0);
        }

        public long solve() {
            if (!solved) {
                minCut = isap.send((long) 1e18);
                solved = true;
            }
            return sumOfPositive - minCut;
        }

        public boolean[] getStatus() {
            if (status == null) {
                solve();
                status = new boolean[n];
                for (LongISAP.Node node : isap.getComponentS()) {
                    if (node.getId() < n) {
                        status[node.getId()] = true;
                    }
                }
            }
            return status;
        }

    }

    static class Edge {
        Node a;
        Node b;
        int id;

        Node other(Node x) {
            return x == a ? b : a;
        }

    }

    static class FastOutput implements AutoCloseable, Closeable {
        private StringBuilder cache = new StringBuilder(10 << 20);
        private final Writer os;

        public FastOutput(Writer os) {
            this.os = os;
        }

        public FastOutput(OutputStream os) {
            this(new OutputStreamWriter(os));
        }

        public FastOutput append(char c) {
            cache.append(c);
            return this;
        }

        public FastOutput append(int c) {
            cache.append(c);
            return this;
        }

        public FastOutput println(int c) {
            cache.append(c).append('\n');
            return this;
        }

        public FastOutput println() {
            cache.append('\n');
            return this;
        }

        public FastOutput flush() {
            try {
                os.append(cache);
                os.flush();
                cache.setLength(0);
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
            return this;
        }

        public void close() {
            flush();
            try {
                os.close();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
        }

        public String toString() {
            return cache.toString();
        }

    }

    static class LongISAP {
        LongISAP.Node[] nodes;
        int[] distanceCnt;
        LongISAP.Node source;
        LongISAP.Node target;
        int nodeNum;
        Map<Long, LongISAP.DirectChannel> channelMap = new HashMap();
        Deque<LongISAP.Node> deque;
        long totalFlow;

        public List<LongISAP.Node> getComponentS() {
            List<LongISAP.Node> result = new ArrayList();
            for (int i = 0; i < nodeNum; i++) {
                nodes[i].visited = false;
            }
            deque.addLast(source);
            source.visited = true;
            while (!deque.isEmpty()) {
                LongISAP.Node head = deque.removeFirst();
                result.add(head);
                for (LongISAP.Channel channel : head.channelList) {
                    if (channel.getFlow() == channel.getCapacity()) {
                        continue;
                    }
                    LongISAP.Node node = channel.getDst();
                    if (node.visited) {
                        continue;
                    }
                    node.visited = true;
                    deque.addLast(node);
                }
            }
            return result;
        }

        private Collection<LongISAP.DirectChannel> getChannels() {
            return channelMap.values();
        }

        private LongISAP.DirectChannel addChannel(int src, int dst) {
            LongISAP.DirectChannel channel = new LongISAP.DirectChannel(nodes[src], nodes[dst], 0, 0);
            nodes[src].channelList.add(channel);
            nodes[dst].channelList.add(channel.getInverse());
            return channel;
        }

        public LongISAP.DirectChannel getChannel(int src, int dst) {
            Long id = (((long) src) << 32) | dst;
            LongISAP.DirectChannel channel = channelMap.get(id);
            if (channel == null) {
                channel = addChannel(src, dst);
                channelMap.put(id, channel);
            }
            return channel;
        }

        public LongISAP(int nodeNum) {
            this.nodeNum = nodeNum;
            deque = new ArrayDeque(nodeNum);
            nodes = new LongISAP.Node[nodeNum];
            distanceCnt = new int[nodeNum + 2];
            for (int i = 0; i < nodeNum; i++) {
                LongISAP.Node node = new LongISAP.Node();
                node.id = i;
                nodes[i] = node;
            }
        }

        public long send(long flow) {
            long sent = 0;
            bfs();
            while (flow > sent && source.distance < nodeNum) {
                sent += send(source, flow - sent);
            }
            totalFlow += sent;
            return sent;
        }

        private long send(LongISAP.Node node, long flowRemain) {
            if (node == target) {
                return flowRemain;
            }

            long sent = 0;
            int nextDistance = node.distance - 1;
            for (LongISAP.Channel channel : node.channelList) {
                long channelRemain = channel.getCapacity() - channel.getFlow();
                LongISAP.Node dst = channel.getDst();
                if (channelRemain == 0 || dst.distance != nextDistance) {
                    continue;
                }
                long actuallySend = send(channel.getDst(), Math.min(flowRemain - sent, channelRemain));
                channel.sendFlow(actuallySend);
                sent += actuallySend;
                if (flowRemain == sent) {
                    break;
                }
            }

            if (sent == 0) {
                if (--distanceCnt[node.distance] == 0) {
                    distanceCnt[source.distance]--;
                    source.distance = nodeNum;
                    distanceCnt[source.distance]++;
                    if (node != source) {
                        distanceCnt[++node.distance]++;
                    }
                } else {
                    distanceCnt[++node.distance]++;
                }
            }

            return sent;
        }

        public void setSource(int id) {
            source = nodes[id];
        }

        public void setTarget(int id) {
            target = nodes[id];
        }

        private void bfs() {
            Arrays.fill(distanceCnt, 0);
            deque.clear();

            for (int i = 0; i < nodeNum; i++) {
                nodes[i].distance = nodeNum;
            }

            target.distance = 0;
            deque.addLast(target);

            while (!deque.isEmpty()) {
                LongISAP.Node head = deque.removeFirst();
                distanceCnt[head.distance]++;
                for (LongISAP.Channel channel : head.channelList) {
                    LongISAP.Channel inverse = channel.getInverse();
                    if (inverse.getCapacity() == inverse.getFlow()) {
                        continue;
                    }
                    LongISAP.Node dst = channel.getDst();
                    if (dst.distance != nodeNum) {
                        continue;
                    }
                    dst.distance = head.distance + 1;
                    deque.addLast(dst);
                }
            }
        }

        public String toString() {
            StringBuilder builder = new StringBuilder();
            for (LongISAP.DirectChannel channel : getChannels()) {
                if (channel.getFlow() == 0) {
                    continue;
                }
                builder.append(channel).append('\n');
            }

            for (LongISAP.DirectChannel channel : getChannels()) {
                if (channel.getFlow() != 0) {
                    continue;
                }
                builder.append(channel).append('\n');
            }
            return builder.toString();
        }

        public static interface Channel {
            public LongISAP.Node getSrc();

            public LongISAP.Node getDst();

            public long getCapacity();

            public long getFlow();

            public void sendFlow(long volume);

            public LongISAP.Channel getInverse();

        }

        public static class DirectChannel implements LongISAP.Channel {
            final LongISAP.Node src;
            final LongISAP.Node dst;
            final int id;
            long capacity;
            long flow;
            LongISAP.Channel inverse;

            public DirectChannel(LongISAP.Node src, LongISAP.Node dst, int capacity, int id) {
                this.src = src;
                this.dst = dst;
                this.capacity = capacity;
                this.id = id;
                inverse = new LongISAP.InverseChannelWrapper(this);
            }

            public void reset(long cap, long flow) {
                this.flow = flow;
                this.capacity = cap;
            }

            public String toString() {
                return String.format("%s--%s/%s-->%s", getSrc(), getFlow(), getCapacity(), getDst());
            }

            public LongISAP.Node getSrc() {
                return src;
            }

            public LongISAP.Channel getInverse() {
                return inverse;
            }

            public LongISAP.Node getDst() {
                return dst;
            }

            public long getCapacity() {
                return capacity;
            }

            public long getFlow() {
                return flow;
            }

            public void sendFlow(long volume) {
                flow += volume;
            }

        }

        public static class InverseChannelWrapper implements LongISAP.Channel {
            final LongISAP.Channel channel;

            public InverseChannelWrapper(LongISAP.Channel channel) {
                this.channel = channel;
            }

            public LongISAP.Channel getInverse() {
                return channel;
            }

            public LongISAP.Node getSrc() {
                return channel.getDst();
            }

            public LongISAP.Node getDst() {
                return channel.getSrc();
            }

            public long getCapacity() {
                return channel.getFlow();
            }

            public long getFlow() {
                return 0;
            }

            public void sendFlow(long volume) {
                channel.sendFlow(-volume);
            }

            public String toString() {
                return String.format("%s--%s/%s-->%s", getSrc(), getFlow(), getCapacity(), getDst());
            }

        }

        public static class Node {
            int id;
            int distance;
            boolean visited;
            List<LongISAP.Channel> channelList = new ArrayList(1);

            public int getId() {
                return id;
            }

            public String toString() {
                return "" + id;
            }

        }

    }

    static class LcaOnTree {
        int[] parent;
        int[] preOrder;
        int[] i;
        int[] head;
        int[] a;
        int time;

        void dfs1(MultiWayIntegerStack tree, int u, int p) {
            parent[u] = p;
            i[u] = preOrder[u] = time++;
            for (IntegerIterator iterator = tree.iterator(u); iterator.hasNext(); ) {
                int v = iterator.next();
                if (v == p) continue;
                dfs1(tree, v, u);
                if (Integer.lowestOneBit(i[u]) < Integer.lowestOneBit(i[v])) {
                    i[u] = i[v];
                }
            }
            head[i[u]] = u;
        }

        void dfs2(MultiWayIntegerStack tree, int u, int p, int up) {
            a[u] = up | Integer.lowestOneBit(i[u]);
            for (IntegerIterator iterator = tree.iterator(u); iterator.hasNext(); ) {
                int v = iterator.next();
                if (v == p) continue;
                dfs2(tree, v, u, a[u]);
            }
        }

        public LcaOnTree(MultiWayIntegerStack tree, int root) {
            int n = tree.stackNumber();
            preOrder = new int[n];
            i = new int[n];
            head = new int[n];
            a = new int[n];
            parent = new int[n];

            dfs1(tree, root, -1);
            dfs2(tree, root, -1, 0);
        }

        private int enterIntoStrip(int x, int hz) {
            if (Integer.lowestOneBit(i[x]) == hz)
                return x;
            int hw = 1 << CachedLog2.floorLog(a[x] & (hz - 1));
            return parent[head[i[x] & -hw | hw]];
        }

        public int lca(int x, int y) {
            int hb = i[x] == i[y] ? Integer.lowestOneBit(i[x]) : (1 << CachedLog2.floorLog(i[x] ^ i[y]));
            int hz = Integer.lowestOneBit(a[x] & a[y] & -hb);
            int ex = enterIntoStrip(x, hz);
            int ey = enterIntoStrip(y, hz);
            return preOrder[ex] < preOrder[ey] ? ex : ey;
        }

    }

    static class SequenceUtils {
        public static boolean equal(int[] a, int al, int ar, int[] b, int bl, int br) {
            if ((ar - al) != (br - bl)) {
                return false;
            }
            for (int i = al, j = bl; i <= ar; i++, j++) {
                if (a[i] != b[j]) {
                    return false;
                }
            }
            return true;
        }

    }

    static class MultiWayIntegerStack {
        private int[] values;
        private int[] next;
        private int[] heads;
        private int alloc;
        private int stackNum;

        public IntegerIterator iterator(final int queue) {
            return new IntegerIterator() {
                int ele = heads[queue];


                public boolean hasNext() {
                    return ele != 0;
                }


                public int next() {
                    int ans = values[ele];
                    ele = next[ele];
                    return ans;
                }
            };
        }

        private void doubleCapacity() {
            int newSize = Math.max(next.length + 10, next.length * 2);
            next = Arrays.copyOf(next, newSize);
            values = Arrays.copyOf(values, newSize);
        }

        public void alloc() {
            alloc++;
            if (alloc >= next.length) {
                doubleCapacity();
            }
            next[alloc] = 0;
        }

        public int stackNumber() {
            return stackNum;
        }

        public MultiWayIntegerStack(int qNum, int totalCapacity) {
            values = new int[totalCapacity + 1];
            next = new int[totalCapacity + 1];
            heads = new int[qNum];
            stackNum = qNum;
        }

        public void addLast(int qId, int x) {
            alloc();
            values[alloc] = x;
            next[alloc] = heads[qId];
            heads[qId] = alloc;
        }

        public String toString() {
            StringBuilder builder = new StringBuilder();
            for (int i = 0; i < stackNum; i++) {
                builder.append(i).append(": ");
                for (IntegerIterator iterator = iterator(i); iterator.hasNext(); ) {
                    builder.append(iterator.next()).append(",");
                }
                if (builder.charAt(builder.length() - 1) == ',') {
                    builder.setLength(builder.length() - 1);
                }
                builder.append('\n');
            }
            return builder.toString();
        }

    }

    static interface IntegerIterator {
        boolean hasNext();

        int next();

    }
}