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.BufferedReader;
import java.io.FileReader;
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.util.Scanner; 
import java.util.StringTokenizer; 
import java.util.*;
import java.io.*;
public class codeforces 
{ 
   static class Student{
       int x,y;//z;
        Student(int x,int y){
            this.x=x;
            this.y=y;
            //this.z=z;
        }
    }
    static int prime[];
    static void sieveOfEratosthenes(int n) 
    { 
        // Create a boolean array "prime[0..n]" and initialize 
        // all entries it as true. A value in prime[i] will 
        // finally be false if i is Not a prime, else true. 
        int pos=0;
        prime= new int[n+1]; 
        for(int p = 2; p*p <=n; p++) 
        { 
            // If prime[p] is not changed, then it is a prime 
            if(prime[p] == 0)
            { 
                // Update all multiples of p
                prime[p]=p;
                for(int i = p*p; i <= n; i += p)
                    if(prime[i]==0)
                    prime[i] = p; 
            } 
        } 
    }
static    class Sortbyroll implements Comparator<Student> 
{ 
    // Used for sorting in ascending order of 
    // roll number 
    public int compare(Student c, Student b) 
    {
        if(c.x<b.x)
            return c.x-b.x;
        if(b.x<c.x)
            return 1;
        return c.y - b.y;
    } 
} 
static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    } 
 
    static class Edge{
        int a,b;
        Edge(int a,int b){
            this.a=a;
            this.b=b;
        }
    }
    static class Trie{
        HashMap<Character,Trie>map;
         int c;
        Trie(){
            map=new HashMap<>();
            //z=null;
            //o=null;
            c=0;
        }
    }
    //static long ans;
    static int parent[];
    static int rank[];
   // static int b[][];
    static int bo[][];
    static int ho[][];
    static int seg[];
    //static int pos;
    static long mod=1000000000+7;
    //static int dp[][];
    static HashMap<String,Integer>map;
    static PriorityQueue<Student>q=new PriorityQueue<>();
    //static Stack<Integer>st;
   // static ArrayList<Character>ans;
    static ArrayList<ArrayList<Integer>>adj;
    //static long ans;
    static int pos;
    static Trie root;
    static long fac[];
    static int gw,gb;
    //static long mod=(long)(998244353);
    static long ans;
    static void solve()throws IOException{
        FastReader sc=new FastReader();
        int n,m,i,j,k,c,pos,x,y;
        n=sc.nextInt();
        m=sc.nextInt();
        int adj[][]=new int[n][n];
        int b[]=new int[n];
        for(i=0;i<m;i++){
            x=sc.nextInt()-1;
            y=sc.nextInt()-1;
            adj[x][y]=1;
            adj[y][x]=1;
        }
        //HashMap<Integer,Integer>map=new HashMap<>();
        ArrayList<Integer>a=new ArrayList<>();
        c=0;
        int p[]=new int[n];
        for(i=0;i<n;i++)
            p[i]=-1;
        for(i=0;i<n;i++){
            if(p[i]!=-1)
                continue;
            //System.out.println(i);
            ++c;
            a.add(i);
            p[i]=i;
            for(j=0;j<n;j++){
                pos=0;
                x=0;
                if(j==i||adj[i][j]==0)
                    continue;
                for(k=0;k<n;k++){
                    if(k==j||k==i)
                        continue;
                    ++x;
                    if((adj[i][k]==1&&adj[j][k]==0)||(adj[i][k]==0&&adj[j][k]==1))
                       {
                           pos=1;
                           break;
                       }
                }
                if(pos==0)
                    p[j]=i;
            }
        }
       // System.out.println(adj[3][1]);
        if(c>3)
            System.out.println("No");
        else{
            //System.out.println(c);
            if(c==0){
                if(n==1){
                    System.out.println("Yes");
                    System.out.print("a");
                }
                else if(n==2){
                    System.out.println("Yes");
                    System.out.print("ac");
                }
                else
                    System.out.print("No");
            }
            else if(c==1){
                System.out.println("Yes");
                for(i=0;i<n;i++){
                    System.out.print("a");
                }
            }
            else if(c==2){
                if(adj[a.get(0)][a.get(1)]==1)
                    System.out.println("No");
                else{
                    System.out.println("Yes");
                    for(i=0;i<n;i++){
                        if(p[i]==a.get(0))
                            System.out.print("a");
                        else
                            System.out.print("c");
                    }
                }
            }
            else{
                if(adj[a.get(0)][a.get(1)]==1&&adj[a.get(0)][a.get(2)]==1&&adj[a.get(1)][a.get(2)]==0){
                    System.out.println("Yes");
                    for(i=0;i<n;i++){
                        if(p[i]==a.get(0))
                            System.out.print("b");
                        else if(p[i]==a.get(1))
                            System.out.print("a");
                        else
                            System.out.print("c");
                    }
                }
                else if(adj[a.get(0)][a.get(1)]==1&&adj[a.get(1)][a.get(2)]==1&&adj[a.get(0)][a.get(2)]==0){
                    System.out.println("Yes");
                    for(i=0;i<n;i++){
                        if(p[i]==a.get(1))
                            System.out.print("b");
                        else if(p[i]==a.get(0))
                            System.out.print("a");
                        else
                            System.out.print("c");
                    }
                }
                else if(adj[a.get(0)][a.get(1)]==0&&adj[a.get(1)][a.get(2)]==1&&adj[a.get(0)][a.get(2)]==1){
                    System.out.println("Yes");
                    for(i=0;i<n;i++){
                        if(p[i]==a.get(2))
                            System.out.print("b");
                        else if(p[i]==a.get(0))
                            System.out.print("a");
                        else
                            System.out.print("c");
                    }
                }
                else
                    System.out.println("No");
            }
        }
    }
    static double dist(long x,long y,long z,long w){
        return Math.sqrt((x-y)*(x-y)+(z-w)*(z-w));
    }
    static double tr(int w,int b,double dp[][]){
        if(w<=0){
            //dp[w][b]=0.0;
            return 0.0;
        }
        if(b<=0){
            //dp[w][b]=1.0;
            return 1.0;
        }
        if(dp[w][b]!=-1.0)
            return dp[w][b];
        if(b<2){
            double ans=((double)w/(double)(w+b));
            dp[w][b]=ans;
            return ans;
        }
        double ans=(double)w/(double)(w+b)+((double)b/(double)(w+b))*((double)(b-1)/(double)(w+b-1))*(((double)w/(double)(w+b-2))*tr(w-1,b-2,dp)+((double)(b-2)/(double)(w+b-2))*tr(w,b-3,dp));
        dp[w][b]=ans;
        return dp[w][b];
    }
    static void update(int s,int e,int l,int r,int i,int seg[][],int lazy[][],int in){
        if(lazy[i][in]!=0){
            seg[i][in]+=1;
            if(s!=e){
                lazy[i][2*in+1]=1;
                lazy[i][2*in+2]=1;
            }
            lazy[i][in]=0;
        }
        if(s>r||l>e||s>e)
            return;
        if(l<=s&&e<=r){
            seg[i][in]+=1;
            if(s!=e){
                lazy[i][2*in+1]=1;
                lazy[i][2*in+2]=1;
            }
            return;
        }
        int mid=(s+e)/2;
        update(s,mid,l,r,i,seg,lazy,2*in+1);
        update(mid+1,e,l,r,i,seg,lazy,2*in+2);
        seg[i][in]=seg[i][2*in+1]+seg[i][2*in+2];
    }
       static int query(int s,int e,int l,int r,int i,int seg[][],int lazy[][],int in){
        if(lazy[i][in]!=0){
            seg[i][in]+=1;
            if(s!=e){
                //System.out.println(s+" "+e+" "+in);
                lazy[i][2*in+1]=1;
                lazy[i][2*in+2]=1;
            }
            lazy[i][in]=0;
        }
        if(s>r||l>e||s>e)
            return Integer.MAX_VALUE;
        if(s>=l&&e<=r){
            return seg[i][in];
        }
        int mid=(s+e)/2;
        return Math.min(query(s,mid,l,r,i,seg,lazy,2*in+1),
        query(mid+1,e,l,r,i,seg,lazy,2*in+2));
        //seg[in]=seg[2*in+1]+seg[2*in+2];
    }
    static boolean isSafe(int x,int y,int b[][],String s[] ){
        if(x>=0&&x<b.length&&y>=0&&y<b[0].length&&s[x].charAt(y)=='#'&&b[x][y]==0)
            return true;
        return false;
    }
    static void add(int x,int y,Queue<Integer>q,Queue<Integer>v,int b[][]){
        q.add(x);
        v.add(y);
        b[x][y]=1;
    }
    static long nCr(long n, long r, 
                                    long p) 
    { 
        return (fac[(int)n]* modInverse(fac[(int)r], p) 
                % p * modInverse(fac[(int)(n-r)], p) 
                                    % p) % p; 
    } 
    //static int prime[];
    //static int dp[];
    public static void main(String[] args){
        //long sum=0;
        try {
                codeforces.solve();
                } catch (Exception e) {
                    e.printStackTrace();
                }
    }
       static long modInverse(long n, long p) 
    { 
        return power(n, p-(long)2,p); 
    } 
 static long power(long x, long y, long p) 
{ 
    long res = 1;      // Initialize result 
  
    x = x % p;  // Update x if it is more than or  
                // equal to p 
  
    while (y > 0) 
    { 
        // If y is odd, multiply x with result 
        if (y %(long)2!=0) 
            res = (res*x) % p; 
  
        // y must be even now 
        y = y>>1; // y = y/2 
        x = (x*x) % p;   
    } 
    return res%p;
 }
    /*public static long power(long x,long a) {
		if(a==0) return 1;
		if(a%2==1)return (x*1L*power(x,a-1))%mod;
		return (power((int)((x*1L*x)%mod),a/2))%mod;
	}*/
   static int find(int x) 
    { 
        // Finds the representative of the set 
        // that x is an element of 
        while(parent[x]!=x) 
        { 
            // if x is not the parent of itself 
            // Then x is not the representative of 
            // his set,
            x=parent[x];
  
            // so we recursively call Find on its parent 
            // and move i's node directly under the 
            // representative of this set 
        } 
  
        return x; 
    }
    static void union(int x, int y) 
    { 
        // Find representatives of two sets 
        int xRoot = find(x), yRoot = find(y); 
  
        // Elements are in the same set, no need 
        // to unite anything. 
        if (xRoot == yRoot) 
            return; 
  
         // If x's rank is less than y's rank 
        if (rank[xRoot] < rank[yRoot]) 
  
            // Then move x under y  so that depth 
            // of tree remains less 
            parent[xRoot] = yRoot; 
  
        // Else if y's rank is less than x's rank 
        else if (rank[yRoot] < rank[xRoot]) 
  
            // Then move y under x so that depth of 
            // tree remains less 
            parent[yRoot] = xRoot; 
  
        else // if ranks are the same 
        { 
            // Then move y under x (doesn't matter 
            // which one goes where) 
            parent[yRoot] = xRoot; 
  
            // And increment the the result tree's 
            // rank by 1 
            rank[xRoot] = rank[xRoot] + 1; 
        } 
    } 
    static long gcd(long a, long b) 
    { 
        if (a == 0){ 
             //ans+=b;
            return b;
        }
        return gcd(b % a, a); 
    }
}