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.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.io.InputStream;
import java.io.BufferedWriter;
import java.io.Writer;
import java.io.OutputStreamWriter;
import java.io.IOException;
import java.util.InputMismatchException;
import java.util.TreeSet;
import java.io.PrintWriter;
import java.io.OutputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author Alex
 */
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);
        TaskC solver = new TaskC();
        solver.solve(1, in, out);
        out.close();
    }
    static class TaskC {
        public void solve(int testNumber, InputReader in, OutputWriter out) {
            int verticies = in.readInt(); //500
            int edges = in.readInt();
            IntIntPair[] input = new IntIntPair[edges];
            TreeSet<IntIntPair> inputts = new TreeSet<>();
            int[] count = new int[verticies];
            for(int i = 0; i < edges; i++) {
                int a = in.readInt() - 1, b = in.readInt() - 1;
                count[a]++;
                count[b]++;
                IntIntPair p = new IntIntPair(Math.min(a, b), Math.max(a, b));
                input[i] = p;
                inputts.add(p);
            }
            ArrayList<Integer>[] adj = new ArrayList[verticies];
            for(int i = 0; i < adj.length; i++) adj[i] = new ArrayList<>();
            for(int i = 0; i < verticies; i++) {
                for(int j = i + 1; j < verticies; j++) {
                    if(!inputts.contains(new IntIntPair(i, j))) {
                        adj[i].add(j);
                        adj[j].add(i);
                    }
                }
            }
            int[] marked = new int[verticies];
            for(int start = 0; start < verticies; start++)
                if(count[start] < verticies - 1) {
//        for(int start = 0; start < verticies; start++) {

                    if(marked[start] == 0) {
                        boolean worked = dfs(start, 1, adj, marked);
                        if(!worked) {
                            out.printLine("No");
                            return;
                        }
                    }
                }
            for(int i = 0; i < verticies; i++) if(marked[i] == 0) marked[i] = 2;
//        out.printLine(marked);
            for(IntIntPair p : inputts) {
                if(Math.abs(marked[p.first] - marked[p.second]) > 1) {
                    out.printLine("No");
                    return;
                }
            }
            StringBuilder res = new StringBuilder();
            for(int val : marked) res.append((char) (val + 'a' - 1));
            out.printLine("Yes");
            out.printLine(res.toString());


        }

        int convert(int a) {
            if(a == 1) return 3;
            if(a == 3) return 1;
            throw new RuntimeException();
        }

        boolean dfs(int cur, int what, ArrayList<Integer>[] adj, int[] marked) {
            if(marked[cur] != 0) return marked[cur] == what;
            marked[cur] = what;
            for(int nxt : adj[cur]) {
                if(!dfs(nxt, convert(what), adj, marked)) return false;
            }
            return true;
        }

    }

    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 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(Object... objects) {
            print(objects);
            writer.println();
        }

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

    }

    static class IntIntPair implements Comparable<IntIntPair> {
        public final int first;
        public final int second;

        public IntIntPair(int first, int second) {
            this.first = first;
            this.second = second;
        }


        public boolean equals(Object o) {
            if(this == o) return true;
            if(o == null || getClass() != o.getClass()) return false;

            IntIntPair pair = (IntIntPair) o;

            return first == pair.first && second == pair.second;

        }


        public int hashCode() {
            int result = Integer.hashCode(first);
            result = 31 * result + Integer.hashCode(second);
            return result;
        }


        public String toString() {
            return "(" + first + "," + second + ")";
        }

        @SuppressWarnings({"unchecked"})
        public int compareTo(IntIntPair o) {
            int value = Integer.compare(first, o.first);
            if(value != 0) {
                return value;
            }
            return Integer.compare(second, o.second);
        }

    }
}

