One day student Vasya was sitting on a lecture and mentioned a string s1s2... sn, consisting of letters "a", "b" and "c" that was written on his desk. As the lecture was boring, Vasya decided to complete the picture by composing a graph G with the following properties: 

  * G has exactly n vertices, numbered from 1 to n. 
  * For all pairs of vertices i and j, where i ≠ j, there is an edge connecting them if and only if characters si and sj are either equal or neighbouring in the alphabet. That is, letters in pairs "a"-"b" and "b"-"c" are neighbouring, while letters "a"-"c" are not. 



Vasya painted the resulting graph near the string and then erased the string. Next day Vasya's friend Petya came to a lecture and found some graph at his desk. He had heard of Vasya's adventure and now he wants to find out whether it could be the original graph G, painted by Vasya. In order to verify this, Petya needs to know whether there exists a string s, such that if Vasya used this s he would produce the given graph G.

Input

The first line of the input contains two integers n and m <image> — the number of vertices and edges in the graph found by Petya, respectively.

Each of the next m lines contains two integers ui and vi (1 ≤ ui, vi ≤ n, ui ≠ vi) — the edges of the graph G. It is guaranteed, that there are no multiple edges, that is any pair of vertexes appear in this list no more than once.

Output

In the first line print "Yes" (without the quotes), if the string s Petya is interested in really exists and "No" (without the quotes) otherwise.

If the string s exists, then print it on the second line of the output. The length of s must be exactly n, it must consist of only letters "a", "b" and "c" only, and the graph built using this string must coincide with G. If there are multiple possible answers, you may print any of them.

Examples

Input

2 1
1 2


Output

Yes
aa


Input

4 3
1 2
1 3
1 4


Output

No

Note

In the first sample you are given a graph made of two vertices with an edge between them. So, these vertices can correspond to both the same and adjacent letters. Any of the following strings "aa", "ab", "ba", "bb", "bc", "cb", "cc" meets the graph's conditions. 

In the second sample the first vertex is connected to all three other vertices, but these three vertices are not connected with each other. That means that they must correspond to distinct letters that are not adjacent, but that is impossible as there are only two such letters: a and c.
import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Iterator;
import java.io.BufferedWriter;
import java.util.InputMismatchException;
import java.io.IOException;
import java.util.Random;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.util.NoSuchElementException;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Egor Kulikov (egor@egork.net)
 */
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);
        TaskA solver = new TaskA();
        solver.solve(1, in, out);
        out.close();
    }

    static class TaskA {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int n = in.readInt();
            int m = in.readInt();
            int[] u = new int[m];
            int[] v = new int[m];
            IOUtils.readIntArrays(in, u, v);
            if (m == n * (n - 1) / 2) {
                out.printLine("Yes");
                for (int i = 0; i < n; i++) {
                    out.print('a');
                }
                out.printLine();
                return;
            }
            boolean[][] edge = new boolean[n][n];
            MiscUtils.decreaseByOne(u, v);
            for (int i = 0; i < m; i++) {
                edge[u[i]][v[i]] = edge[v[i]][u[i]] = true;
            }
            for (int i = 0; i < n; i++) {
                edge[i][i] = true;
            }
            int one = -1;
            int two = -1;
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < i; j++) {
                    if (!edge[i][j]) {
                        one = i;
                        two = j;
                    }
                }
            }
            IntSet first = new IntHashSet();
            IntSet second = new IntHashSet();
            for (int i = 0; i < n; i++) {
                if (!edge[i][one]) {
                    first.add(i);
                } else if (!edge[i][two]) {
                    second.add(i);
                }
            }
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < i; j++) {
                    boolean noEdge = first.contains(i) && second.contains(j) || first.contains(j) && second.contains(i);
                    if (noEdge == edge[i][j]) {
                        out.printLine("No");
                        return;
                    }
                }
            }
            out.printLine("Yes");
            for (int i = 0; i < n; i++) {
                if (first.contains(i)) {
                    out.print('a');
                } else if (second.contains(i)) {
                    out.print('c');
                } else {
                    out.print('b');
                }
            }
            out.printLine();
        }
    }

    static class IntHash {
        private IntHash() {
        }

        public static int hash(int c) {
            return c;
        }
    }

    static class MiscUtils {
        public static void decreaseByOne(int[]... arrays) {
            for (int[] array : arrays) {
                for (int i = 0; i < array.length; i++) {
                    array[i]--;
                }
            }
        }
    }

    static class IOUtils {
        public static void readIntArrays(InputReader in, int[]... arrays) {
            for (int i = 0; i < arrays[0].length; i++) {
                for (int j = 0; j < arrays.length; j++) {
                    arrays[j][i] = in.readInt();
                }
            }
        }
    }

    static class IntArray extends IntAbstractStream implements IntList {
        private int[] data;

        public IntArray(int[] arr) {
            data = arr;
        }

        public int size() {
            return data.length;
        }

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

        public void addAt(int index, int value) {
            throw new UnsupportedOperationException();
        }

        public void removeAt(int index) {
            throw new UnsupportedOperationException();
        }
    }

    static interface IntIterator {
        public int value() throws NoSuchElementException;

        public boolean advance();

        public boolean isValid();
    }

    static class IntHashSet extends IntAbstractStream implements IntSet {
        private static final Random RND = new Random();
        private static final int[] SHIFTS = new int[4];
        private static final byte PRESENT_MASK = 1;
        private static final byte REMOVED_MASK = 2;
        private int size;
        private int realSize;
        private int[] values;
        private byte[] present;
        private int step;
        private int ratio;

        static {
            for (int i = 0; i < 4; i++) {
                SHIFTS[i] = RND.nextInt(31) + 1;
            }
        }

        public IntHashSet() {
            this(3);
        }

        public IntHashSet(int capacity) {
            capacity = Math.max(capacity, 3);
            values = new int[capacity];
            present = new byte[capacity];
            ratio = 2;
            initStep(capacity);
        }

        public IntHashSet(IntCollection c) {
            this(c.size());
            addAll(c);
        }

        public IntHashSet(int[] arr) {
            this(new IntArray(arr));
        }

        private void initStep(int capacity) {
            step = RND.nextInt(capacity - 2) + 1;
            while (IntegerUtils.gcd(step, capacity) != 1) {
                step++;
            }
        }

        public IntIterator intIterator() {
            return new IntIterator() {
                private int position = size == 0 ? values.length : -1;

                public int value() throws NoSuchElementException {
                    if (position == -1) {
                        advance();
                    }
                    if (position >= values.length) {
                        throw new NoSuchElementException();
                    }
                    if ((present[position] & PRESENT_MASK) == 0) {
                        throw new IllegalStateException();
                    }
                    return values[position];
                }

                public boolean advance() throws NoSuchElementException {
                    if (position >= values.length) {
                        throw new NoSuchElementException();
                    }
                    position++;
                    while (position < values.length && (present[position] & PRESENT_MASK) == 0) {
                        position++;
                    }
                    return isValid();
                }

                public boolean isValid() {
                    return position < values.length;
                }

                public void remove() {
                    if ((present[position] & PRESENT_MASK) == 0) {
                        throw new IllegalStateException();
                    }
                    present[position] = REMOVED_MASK;
                }
            };
        }

        public int size() {
            return size;
        }

        public void add(int value) {
            ensureCapacity((realSize + 1) * ratio + 2);
            int current = getHash(value);
            while (present[current] != 0) {
                if ((present[current] & PRESENT_MASK) != 0 && values[current] == value) {
                    return;
                }
                current += step;
                if (current >= values.length) {
                    current -= values.length;
                }
            }
            while ((present[current] & PRESENT_MASK) != 0) {
                current += step;
                if (current >= values.length) {
                    current -= values.length;
                }
            }
            if (present[current] == 0) {
                realSize++;
            }
            present[current] = PRESENT_MASK;
            values[current] = value;
            size++;
        }

        private int getHash(int value) {
            int hash = IntHash.hash(value);
            int result = hash;
            for (int i : SHIFTS) {
                result ^= hash >> i;
            }
            result %= values.length;
            if (result < 0) {
                result += values.length;
            }
            return result;
        }

        private void ensureCapacity(int capacity) {
            if (values.length < capacity) {
                capacity = Math.max(capacity * 2, values.length);
                rebuild(capacity);
            }
        }

        private void rebuild(int capacity) {
            initStep(capacity);
            int[] oldValues = values;
            byte[] oldPresent = present;
            values = new int[capacity];
            present = new byte[capacity];
            size = 0;
            realSize = 0;
            for (int i = 0; i < oldValues.length; i++) {
                if ((oldPresent[i] & PRESENT_MASK) == PRESENT_MASK) {
                    add(oldValues[i]);
                }
            }
        }

        public boolean contains(int value) {
            int current = getHash(value);
            while (present[current] != 0) {
                if (values[current] == value && (present[current] & PRESENT_MASK) != 0) {
                    return true;
                }
                current += step;
                if (current >= values.length) {
                    current -= values.length;
                }
            }
            return false;
        }
    }

    static interface IntCollection extends IntStream {
        public int size();

        default public void add(int value) {
            throw new UnsupportedOperationException();
        }

        default public IntCollection addAll(IntStream values) {
            for (IntIterator it = values.intIterator(); it.isValid(); it.advance()) {
                add(it.value());
            }
            return this;
        }
    }

    static interface IntSet extends IntCollection {
    }

    static interface IntReversableCollection extends IntCollection {
    }

    static 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);
        }
    }

    static interface IntList extends IntReversableCollection {
        public abstract int get(int index);

        public abstract void addAt(int index, int value);

        public abstract void removeAt(int index);

        default public IntIterator intIterator() {
            return new IntIterator() {
                private int at;
                private boolean removed;

                public int value() {
                    if (removed) {
                        throw new IllegalStateException();
                    }
                    return get(at);
                }

                public boolean advance() {
                    at++;
                    removed = false;
                    return isValid();
                }

                public boolean isValid() {
                    return !removed && at < size();
                }

                public void remove() {
                    removeAt(at);
                    at--;
                    removed = true;
                }
            };
        }

        default public void add(int value) {
            addAt(size(), value);
        }
    }

    static interface IntStream extends Iterable<Integer>, Comparable<IntStream> {
        public IntIterator intIterator();

        default public Iterator<Integer> iterator() {
            return new Iterator<Integer>() {
                private IntIterator it = intIterator();

                public boolean hasNext() {
                    return it.isValid();
                }

                public Integer next() {
                    int result = it.value();
                    it.advance();
                    return result;
                }
            };
        }

        default public int compareTo(IntStream c) {
            IntIterator it = intIterator();
            IntIterator jt = c.intIterator();
            while (it.isValid() && jt.isValid()) {
                int i = it.value();
                int j = jt.value();
                if (i < j) {
                    return -1;
                } else if (i > j) {
                    return 1;
                }
                it.advance();
                jt.advance();
            }
            if (it.isValid()) {
                return 1;
            }
            if (jt.isValid()) {
                return -1;
            }
            return 0;
        }

        default public boolean contains(int value) {
            for (IntIterator it = intIterator(); it.isValid(); it.advance()) {
                if (it.value() == value) {
                    return true;
                }
            }
            return false;
        }
    }

    static class IntegerUtils {
        public static int gcd(int a, int b) {
            a = Math.abs(a);
            b = Math.abs(b);
            while (b != 0) {
                int temp = a % b;
                a = b;
                b = temp;
            }
            return a;
        }
    }

    static abstract class IntAbstractStream implements IntStream {

        public String toString() {
            StringBuilder builder = new StringBuilder();
            boolean first = true;
            for (IntIterator it = intIterator(); it.isValid(); it.advance()) {
                if (first) {
                    first = false;
                } else {
                    builder.append(' ');
                }
                builder.append(it.value());
            }
            return builder.toString();
        }

        public boolean equals(Object o) {
            if (!(o instanceof IntStream)) {
                return false;
            }
            IntStream c = (IntStream) o;
            IntIterator it = intIterator();
            IntIterator jt = c.intIterator();
            while (it.isValid() && jt.isValid()) {
                if (it.value() != jt.value()) {
                    return false;
                }
                it.advance();
                jt.advance();
            }
            return !it.isValid() && !jt.isValid();
        }

        public int hashCode() {
            int result = 0;
            for (IntIterator it = intIterator(); it.isValid(); it.advance()) {
                result *= 31;
                result += it.value();
            }
            return result;
        }
    }

    static class OutputWriter {
        private final PrintWriter writer;

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

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        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() {
            writer.println();
        }

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

        public void print(char i) {
            writer.print(i);
        }

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

