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.math.BigInteger;
import java.util.*;



 public class Main {
	public static InputReader in;
    public static PrintWriter pw;
	public static void main(String args[]) {
		new Thread(null, new Runnable() {
            public void run() {
                try{
                    solve();
                }
                catch(Exception e){
                    e.printStackTrace();
                }
            }
        }, "1", 1 << 26).start();
    }
	static ArrayList<Integer>[] g;
	static long edje=0;
    static boolean vis[];
	static int parent[];
	static int col[];
	static int val[];
	static int degree[];
	static int f[];
	static boolean visited[];
    static int edjes=0;
    static int a[][];
   static ArrayList<Integer>[] h;
	public static void solve(){
	
		 in = new InputReader(System.in);
		 pw = new PrintWriter(System.out);
	     int n=in.nextInt();
	     int m=in.nextInt();
	     g=new ArrayList[n+1];
	     h=new ArrayList[n+1];
	     for(int i=0;i<=n;i++){
	    	 g[i]=new ArrayList<Integer>();
	         h[i]=new ArrayList<Integer>();
	     }
	     for(int i=1;i<=m;i++)
	     {
	    	 int x=in.nextInt();
	    	 int y=in.nextInt();
	    	 h[x].add(y);
	    	 h[y].add(x);
	     }
	     for(int i=1;i<=n;i++)
	     {
	    	 for(int j=i+1;j<=n;j++)
	    	 {
	    		 if(!h[i].contains(j)){
	    			 g[i].add(j);
	    		     g[j].add(i);
	    		 }
	         }
	     }
	    
	     int root=-1;
	     boolean f=false;
         for(int i=1;i<=n;i++)
         {
        	 for(int j=0;j<g[i].size();j++){
        		 if(!f)
        		 {
        			 f=true;
        			 root=i;
        		 }
        	//	 System.out.println(i+" "+g[i].get(j));
        	 }
         } int lev[]=new int[n+1];
         
         vis=new boolean[n+1];
         if(root!=-1)
         {
         Queue<Integer> Q=new LinkedList<Integer>();
         Q.add(root);
         vis[root]=true;
         lev[root]=1;
        
         while(!Q.isEmpty())
         {
        	 	 int p=Q.poll();
        		 vis[p]=true;
        		 for(int x:g[p])
        		 {
        			if(!vis[x])
        			{
        				Q.add(x);
        				lev[x]=lev[p]+1;
        			}
        		 }	
         }
         }
         char ans[]=new char[n+1];
         
         visited=new boolean[n+1];
         for(int i=1;i<=n;i++)
         {
        	 if(!visited[i]){
        		 dfs2(i);
        	 }
         }
         for(int i=1;i<=n;i++){
        	 if(lev[i]==0)
        	 {
        		 ans[i]='b';
        	 }
        	 else if(lev[i]%2==1)
        	 {
        		 ans[i]='a';
        	 }
        	 else
        		ans[i]='c';
         }
         for(int i=1;i<=n;i++)
         {
        	 for(int j=i+1;j<=n;j++)
        	 {
        		 if(g[i].contains(j))
        		 {
        			 if(ans[i]=='a'&&ans[j]=='c'||(ans[i]=='c'&&ans[j]=='a'))
        				 continue;
        			 else
        			 {
        				 System.out.println("No");
        				 System.exit(0);
        			 }
        		 }
        		 else
        		 {
        			if(ans[i]=='a'&&ans[j]=='c'||(ans[i]=='c'&&ans[j]=='a'))
        			{
        				System.out.println("No");
        				System.exit(0);
        			}
        		 }
        	 }
         }
         System.out.println("Yes");
         for(int i=1;i<=n;i++){
        	 if(lev[i]==0)
        	 {
        		 System.out.print('b');
        	 }
        	 else if(lev[i]%2==1)
        	 {
        		 System.out.print('a');
        	 }
        	 else
        		 System.out.print('c');
         }
	    
	    
	}
	public static void dfs2(int curr){
		
	}
  
/*public static boolean dfs1(int s,int t,int col)
{
	vis[s]=true;
	Stack<Integer> st=new Stack<Integer>();
	st.push(s);
	int temp=0;
	while(!st.isEmpty())
	{
		int top=st.pop();
		for(int p:g[top])
		{
			if(!vis[p]&&two[top][p].contains(col))
			{
				st.push(p);
				vis[p]=true;
			
			if(p==t)
			{
				return true;
			}
			}
		}
		
		}
return false;

}



/*	private static void TopologicalSort() 
	{
		for(int i=0;i<26;i++)
		{
			if(!visited[i]&&g[i].size()!=0)
			{
				dfs(i);
			}
		}
	}
	public static void dfs(int curr)
	{
		visited[curr]=true;
		for(int x:g[curr])
		{
			if(!visited[x])
				dfs(x);
		}
		stack.push(curr);
	}



	/*public static void dfs(int curr)
	{
		vis[curr]=true;
		int trees=0;
		for(int x:g[curr])
		{
			if(!vis[x]&&x!=1)
			{
			trees++;
			if(!s.contains(curr+" "+x))
				total+=cost[curr][x];
			dfs(x);
			}
	    }
		if(trees==0)
		{
			if(!s.contains(curr+" "+1))
				total+=cost[1][curr];
		}
	}
	public static void dfs1(int curr,int parent)
	{
	val[curr]=a[curr];
	for(int x:g[curr])
	{
	       if(x!=parent)
	       {
	    	   dfs1(x,curr);
	    	   val[curr]+=val[x];
	      }
	
	}
	}
	public static void dfs2(int curr,int parent)
	{
		f[curr]=val[curr];
		for(int x:g[curr])
		{
			if(x!=parent)
			{
				dfs2(x,curr);
				f[curr]+=f[x];
			}
		}
	}
	
	
	 
/*    public static void dfs2(int curr)
    {
    if(st[col[curr]].isEmpty())
    {
    ans[curr]=-1;	
    }
    else
    {
    	ans[curr]=st[col[curr]].peek();
    }
    st[col[curr]].push(curr);
    for(int x:g[curr])
    {
    	dfs2(x);
    }
    st[col[curr]].pop();
    	
    }
    
  
	public static void dfs1(int curr)
	{
		visited[curr]=true;
		for(int next:g[curr])
		{
			edje++;
			if(!visited[next])
				dfs1(next);
		}
	}
	
	public static void dfs(int curr,int prev)
		{
		val[curr]=1;
			for(int x:g[curr])
			{
				if(x!=prev)
				{
		            dfs(x,curr);
		            val[curr]+=val[x];
					
			    }
			}
		}*/


		public static long power(long a,long b)
		{
			long result=1;
			while(b>0)
			{
				if(b%2==1)
					result*=a;
				a=a*a;
				b/=2;
			}
			return result;
		}
				public static long pow(long n,long p,long m)
	{
		 long  result = 1;
		  if(p==0)
		    return 1;
		if (p==1)
		    return n;
		while(p!=0)
		{
		    if(p%2==1)
		        result *= n;
		    if(result>=m)
		    result%=m;
		    p >>=1;
		    n*=n;
		    if(n>=m)
		    n%=m;
		}
		return result;
	}
	static class Pair implements Comparable<Pair>{
	int day1;
		int day2;
		int val;
		Pair(int mr,int i){
	     	day1=mr;
	     	day2=i;
			
			
		}
		@Override
		public int compareTo(Pair o) {
		if(o.day1<this.day1)
		
			return 1;
			
			else 
				return -1;
			
			}
		
	}
	public static long gcd(long a, long b) {
		  if (b == 0) return a;
		  return gcd(b, a%b);
		}
	static class InputReader {
 
		private InputStream stream;
		private byte[] buf = new byte[8192];
		private int curChar, snumChars;
		private SpaceCharFilter filter;
 
		public InputReader(InputStream stream) {
			this.stream = stream;
		}
 
		public int snext() {
			if (snumChars == -1)
				throw new InputMismatchException();
			if (curChar >= snumChars) {
				curChar = 0;
				try {
					snumChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (snumChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}
 
		public   int nextInt() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}
 
		public long nextLong() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = snext();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = snext();
			} while (!isSpaceChar(c));
			return res * sgn;
		}
 
		public int[] nextIntArray(int n) {
			int a[] = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}
 
		public String readString() {
			int c = snext();
			while (isSpaceChar(c))
				c = snext();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = snext();
			} while (!isSpaceChar(c));
			return res.toString();
		}
 
		public boolean isSpaceChar(int c) {
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}
 
		public interface SpaceCharFilter {
			public boolean isSpaceChar(int ch);
		}
	}
}
