Paul hates palindromes. He assumes that string s is tolerable if each its character is one of the first p letters of the English alphabet and s doesn't contain any palindrome contiguous substring of length 2 or more.

Paul has found a tolerable string s of length n. Help him find the lexicographically next tolerable string of the same length or else state that such string does not exist.

Input

The first line contains two space-separated integers: n and p (1 ≤ n ≤ 1000; 1 ≤ p ≤ 26). The second line contains string s, consisting of n small English letters. It is guaranteed that the string is tolerable (according to the above definition).

Output

If the lexicographically next tolerable string of the same length exists, print it. Otherwise, print "NO" (without the quotes).

Examples

Input

3 3
cba


Output

NO


Input

3 4
cba


Output

cbd


Input

4 4
abcd


Output

abda

Note

String s is lexicographically larger (or simply larger) than string t with the same length, if there is number i, such that s1 = t1, ..., si = ti, si + 1 > ti + 1.

The lexicographically next tolerable string is the lexicographically minimum tolerable string which is larger than the given one.

A palindrome is a string that reads the same forward or reversed.
import java.io.InputStreamReader;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Dictionary;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Map;
import java.util.StringTokenizer;

import javax.print.attribute.DocAttributeSet;
import javax.print.attribute.HashDocAttributeSet;

import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		PrintWriter out = new PrintWriter(outputStream);
		TaskA solver = new TaskA();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskA {
	boolean[] is_prime;
	int max;
	public void sieve(){
		max = (1<<29)+(1<<27)+(1<<24)+(1<<23);
		//System.out.println(max);
		is_prime = new boolean[max+1];
		is_prime[0] = is_prime[1] = true;
		for(int i = 2; i*i < max; i++){
			if(!is_prime[i]){
				for(int j = i*i; j <= max; j+=i){
					is_prime[j] = true;
				}
			}
		}
	}	 
	
    public void solve(int testNumber, InputReader in, PrintWriter out) {
       int n = in.nextInt() , p = in.nextInt();
       char[] s = in.next().toCharArray();
       
       for(int i = n - 1; i >= 0; i--){
    	   for(char ch = (char) (s[i]+1); ch < 'a'+p; ch++){
    		   s[i] = ch;
    		   if( i >= 1 && s[i] == s[i-1] || i >= 2 && s[i] == s[i-2])
                  continue;
    		   lable:
    		     for(int j = i+1; j < n; j++){
    		    	 for(char sd = 'a'; sd < 'a'+p; sd++){
    		    		   s[j] = sd;
    		    		   if( j >= 1 && s[j] == s[j-1] || j >= 2 && s[j] == s[j-2])
    		                  continue;
    		    		   continue lable;
    		    	 }
    		    }
    		     out.println(new String(s));
    		     return;
    	   }
       }
       out.println("NO");
    }
}



    //||||||| UNION FIND ||||||||
  class uni_find{
	  int[] id , sz;
	  int count ;
	 
	  public uni_find(int N){
		  count = N;
	      id = new int[N];
	      sz = new int [N];
	      for (int i = 0; i < N; i++)
	         id[i] = i;
	      for (int i = 0; i < N; i++)
	    	  sz[i] = 1;
	  }
	  
	  private int find(int p) 
	  {  
	     while (p != id[p]) p = id[p];
	     return p; 
	  }
	  public void union(int p, int q)
	   {  
	      int i = find(p);
	      int j = find(q);
	      if (i == j) return;
	     // Make smaller root point to larger one.
	      if   (sz[i] < sz[j]) { id[i] = j; sz[j] += sz[i]; }
	      else                 { id[j] = i; sz[i] += sz[j]; }
	      count--;
	   }
	  
	  public int count() {
			return count;
		}
		public boolean connected(int p, int q) {
			return find(p) == find(q);
		}
  }
  
  
         //||||||| comparable pair ||||||||
 class pair implements Comparable<pair>{
	 public long first,second;
	 public pair(){
		 first = second = 0;
	 }
	@Override
	public int compareTo(pair arg0) {
		if(this.second > arg0.second)
			return 1;
		else if(this.second < arg0.second)
			return -1;
		else if(this.first > arg0.first)
			return 1;
		else if(this.first < arg0.first)
		     return -1;
		return 0;
	}
 }

 
   // ||||||| INPUT READER ||||||||
class InputReader {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream));
        tokenizer = null;
    }

    public String next() {
        while (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public Integer nextInt() {
        return Integer.parseInt(next());
    }
    
    public Long nextLong() {
    	return Long.parseLong(next());
    }
    
    public Double nextDouble() {
    	return Double.parseDouble(next());
    }
    
    public Float nextFloat() {
    	return Float.parseFloat(next());
    }
    
    public BigInteger nextBigInteger() {
    	return new BigInteger(next());
    }
    
    public String nextLine() {
    	try {
			return reader.readLine();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
    	
    }
    
    public Integer[] nextIntegerArray(int n) {
    	Integer[] a = new Integer[n];
    	for(Integer i = 0; i <  n; i++)
    		a[i] = nextInt();
    	
    	return a;
    }
    
    public Long[] nextLongArray(int n) {
    	Long[] a = new Long[n];
    	for(Integer i = 0; i <  n; i++)
    		a[i] = nextLong();
    	
    	return a;
    }
    
    public long[] nextlongArray(int n) {
    	long[] a = new long[n];
    	for(Integer i = 0; i <  n; i++)
    		a[i] = nextLong();
    	
    	return a;
    }
    
    public double[] nextdoubleArray(int n) {
    	double[] a = new double[n];
    	for(Integer i = 0; i <  n; i++)
    		a[i] = nextDouble();
    	
    	return a;
    }
    
    public String[] nextStringArray(int n){
    	String[] s = new String[n];
    	for(Integer i = 0; i < n; i++)
    		s[i] = next();
    	return s;
    }
    
    public String[] nextLineStringArray(int n){
    	String[] s = new String[n];
    	for(Integer i = 0; i < n; i++)
    		s[i] = next();
    	return s;
    }

    
    }