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.*;
import java.util.Arrays;
import java.util.InputMismatchException;



public class CodeForcesC {
    private static InputReader in = new InputReader(System.in);
    private static OutputWriter out = new OutputWriter(System.out);


    static void solve() throws Exception {
        int n = in.readInt();
        UndirectedGraph ug = new UndirectedGraph(n);
        int m = in.readInt();
        for(int i=0; i<m; ++i){
            int u = in.readInt();
            int v = in.readInt();
            ug.addEdge(u,v);
        }
        char[] str = new char[n+1];
        char last = 'c';

        boolean flag = true;
        int i=1;
        while((flag)&&(i<=n)){
            if(ug.adj[i].size()!= n-1) {
                if (last == 'c') {
                    str[i] = 'a';
                    last = 'a';
                } else {
                    str[i] = 'c';
                    last = 'c';
                }
            

                for( int j=i+1;j<=n; ++j){
                    if(ug.isEdgeExists(i,j)){
                        if(ug.adj[j].size()!= n-1) {
                            str[j] = str[i];
                        }
                        else{
                            str[j] = 'b';
                        }
                    }
                }
                flag = false;
                for( int j=i+1;j<=n; ++j){
                    if(!ug.isEdgeExists(i,j)){
                       flag = true;
                       i= j;
                       break;
                    }

                }
            }
            else{
                str[i] = 'b';
                i++;
            }

        }

        flag = true;
        for(i=1; i<=n; ++i) {
            char a = str[i];
            for (int j = 1; j <= n; ++j) {
                if(i==j){
                    continue;
                }
                char b = str[j];
                if (Math.abs(b - a) == 2) {
                    if (ug.isEdgeExists(i, j)) {
                        flag = false;
                    }
                }
                else{
                    if(!ug.isEdgeExists(i,j)){
                        flag = false;
                    }
                }
            }
        }

        if(flag){
            out.println("Yes");
            for(i=1; i<=n; ++i){
                out.print(str[i]);
            }
            out.println();
        }
        else{
            out.println("No");
        }


    }

    public static void main(String[] args) throws Exception {
        solve();
        out.close();
    }

    private static class Bag{
        private int N;
        private Node first;
        private Node current;
        private static class Node{
            public int value;
            public Node next;

            public Node(int value, Node next){
                this.value = value;
                this.next = next;
            }

        }

        public Bag(){
            first = null;
            N = 0;
            current = null;
        }

        public boolean isEmpty(){
            return first==null;
        }

        public int size(){
            return N;
        }

        public void add(int A){
            Node oldFirst = first;
            first = new Node(A,oldFirst);
            current = first;
            N++;
        }
        public void remove(int A){
            Node n = first;
            if(n.value == A){
                first = n.next;
                current = first;
                N--;
                return;
            }
            else{
                for(int i=1;i<this.size();i++){
                    if(n.next.value==A){
                        n.next = n.next.next;
                        N--;
                        return;
                    }
                    n=n.next;
                }
            }
        }

        public int getNext(){
            int value = current.value;
            current = current.next;
            return value;
        }

        public void reset(){
            current = first;
        }
    }

    private static class UndirectedGraph{
        private int V;
        private int E;
        public Bag[] adj;
        private boolean[][] matrix;

        public UndirectedGraph(int V){
            this.V = V;
            this.E = 0;
            matrix = new boolean[V+1][V+1];
            adj = new Bag[V+1];
            for(int i=1;i<=V; i++){
                adj[i] = new Bag();
            }
        }

        public int V(){
            return V;
        }

        public int E(){
            return E;
        }

        public void addEdge(int A, int B){
            if(!isEdgeExists(A,B)){
                adj[A].add(B);
                adj[B].add(A);
                matrix[A][B] = true;
                matrix[B][A] = true;
                E++;
            }
        }

        public void removeEdge(int A, int B){

            adj[A].remove(B);
            adj[B].remove(A);
            matrix[A][B] = false;
            matrix[B][A] = false;
            E--;
        }

        public boolean isEdgeExists(int A, int B){
            return matrix[A][B];
        }

        public boolean isContains(int A){
            return !(adj[A].isEmpty());
        }


        public int vertexDegree(int A){
            return adj[A].size();
        }

        public boolean isEmpty(){
            return E==0;
        }
    }



    private static class InputReader {
        private InputStream stream;
        private byte[] buffer;
        private int currentIndex;
        private int bytesRead;

        public InputReader(InputStream stream) {
            this.stream = stream;
            buffer = new byte[131072];
        }


        public InputReader(InputStream stream, int bufferSize) {
            this.stream = stream;
            buffer = new byte[bufferSize];
        }


        private int read() throws IOException {
            if (currentIndex >= bytesRead) {
                currentIndex = 0;
                bytesRead = stream.read(buffer);
                if (bytesRead <= 0) {
                    return -1;
                }
            }
            return buffer[currentIndex++];
        }

        public String readString() throws IOException {
            int c = read();
            while (!isPrintable(c)) {
                c = read();
            }
            StringBuilder result = new StringBuilder();
            do {
                result.appendCodePoint(c);
                c = read();
            } while (isPrintable(c));
            return result.toString();
        }

        public int readInt() throws Exception {
            int c = read();
            int sign = 1;
            while (!isPrintable(c)) {
                c = read();
            }
            if (c == '-') {
                sign = -1;
                c = read();
            }
            int result = 0;
            do {
                if ((c < '0') || (c > '9')) {
                    throw new InputMismatchException();
                }
                result *= 10;
                result += (c - '0');
                c = read();
            } while (isPrintable(c));
            return sign * result;
        }

        public long readLong() throws Exception {
            int c = read();
            int sign = 1;
            while (!isPrintable(c)) {
                c = read();
            }
            if (c == '-') {
                sign = -1;
                c = read();
            }
            long result = 0;
            do {
                if ((c < '0') || (c > '9')) {
                    throw new InputMismatchException();
                }
                result *= 10;
                result += (c - '0');
                c = read();
            } while (isPrintable(c));
            return sign * result;
        }

        public double readDouble() throws Exception {
            int c = read();
            int sign = 1;
            while (!isPrintable(c)) {
                c = read();
            }
            if (c == '-') {
                sign = -1;
                c = read();
            }
            boolean fraction = false;
            double multiplier = 1;
            double result = 0;
            do {
                if ((c == 'e') || (c == 'E')) {
                    return sign * result * Math.pow(10, readInt());
                }
                if ((c < '0') || (c > '9')) {
                    if ((c == '.') && (!fraction)) {
                        fraction = true;
                        c = read();
                        continue;
                    }
                    throw new InputMismatchException();
                }
                if (fraction) {
                    multiplier /= 10;
                    result += (c - '0') * multiplier;
                    c = read();
                } else {
                    result *= 10;
                    result += (c - '0');
                    c = read();
                }
            } while (isPrintable(c));
            return sign * result;
        }

        private boolean isPrintable(int c) {
            return ((c > 32) && (c < 127));
        }
    }

    private static class OutputWriter {
        private 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 println(Object... objects) {
            print(objects);
            writer.println();
        }

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

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