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.
/*
 * Remember a 7.0 student can know more than a 10.0 student.
 * Grades don't determine intelligence, they test obedience. 
 * I Never Give Up.
 */
import java.util.*;
import java.util.Map.Entry;
import java.io.*;
import java.text.*;

import static java.lang.System.out;
import static java.util.Arrays.*;
import static java.lang.Math.*;
public class ContestMain {
	private static Reader in=new Reader();
	private static StringBuilder ans=new StringBuilder();
	private static long MOD=1000000007;//10^9+7 
	private static final int N=100000+7; //10^5
//	private static final int LIM=26;
//	private static final double PI=3.1415;
//	private static ArrayList<Integer> v[]=new ArrayList[N];
//	private static int color[]=new int[N];
//	private static boolean mark[]=new boolean[N];
//	private static BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
//	private static void dfs(int node){mark[node]=true;for(int x:v[node]){if(!mark[x]){dfs(x);}}}
	private static long powmod(long x,long n,long m){
		if(n==0)return 1;
		else if(n%2==0)return(powmod((x*x)%m,n/2,m));
		else return (x*(powmod((x*x)%m,(n-1)/2,m)))%m;
	}
//	private static void shuffle(long [] arr) {
//		for (int i = arr.length - 1; i >= 2; i--) {
//			int x = new Random().nextInt(i - 1);
//	        long temp = arr[x];
//	        arr[x] = arr[i];
//	        arr[i] = temp;
//	    }
//	 }
//	private static long gcd(long a, long b){
//		if(b==0)return a;
//		return gcd(b,a%b);
//	}
//	private static boolean check(int x,int y){
//		if((x>=0&&x<n)&&(y>=0&&y<m)&&mat[x][y]!='X'&&!visited[x][y])return true;
//		return false;
//	}
//	static class Node{
//		int x,y,c;
//		Node(int x,int y,int c){
//			this.x=x;
//			this.y=y;
//			this.c=c;
//		}
//	}
	public static void main(String[] args) throws IOException{
		int n=in.nextInt();
		int p=in.nextInt();
		char ar[]=in.next().toCharArray();
		int lim=97+p-1,temp;
		int ind=-1;
		for(int i=n-1;i>=0;i--){
			temp=ar[i]+1;
			while((i-1>=0&&ar[i-1]==temp)||(i-2>=0&&ar[i-2]==temp))temp++;
			if(temp<=lim){
				ar[i]=(char)temp;
				ind=i;
				break;
			}
		}
		if(ind==-1){out.println("NO");return;}
		for(int i=ind+1;i<n;i++){
			temp=97;
			while((i-1>=0&&ar[i-1]==temp)||(i-2>=0&&ar[i-2]==temp))temp++;
			ar[i]=(char) temp;
		}
		for(char ch:ar)
			out.print(ch);
	}
	static class Pair<T> implements Comparable<Pair>{
		int l;
		int r;
		Pair(){
			l=0;
			r=0;
		}
		Pair(int k,int v){
			l=k;
			r=v;
		}
		@Override
		public int compareTo(Pair o) {
			if(o.l!=l)return (int) (l-o.l);
			else return (r-o.r);
		}
		
	}
	static class Reader{
        BufferedReader br;
        StringTokenizer st;
        public Reader()
        {
            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;
        }
    }
}