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.*;
import java.util.*;

/**
 * Created by Katushka on 11.03.2020.
 */
public class Main {

    static int[] readArray(int size, InputReader in, boolean substractOne) {
        int[] a = new int[size];
        for (int i = 0; i < size; i++) {
            a[i] = (in.nextInt() - (substractOne ? 1 : 0));
        }
        return a;
    }

    private static final long MOD = 1000000007;


    public static void main(String[] args) throws FileNotFoundException {
        long start = System.currentTimeMillis();
//
//        InputReader in = new InputReader(new FileInputStream("input2.txt"));
//        PrintWriter out = new PrintWriter(new BufferedOutputStream(new FileOutputStream("greedy.out")));

        InputReader in = new InputReader(System.in);
        PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));

        int n = in.nextInt();
        int p = in.nextInt();
        String s = in.nextString();

        if (p == 1) {
            out.println("NO");
            out.close();
            return;
        }
        if (p == 2) {
            if (n == 2) {
                if (s.equals("ab")) {
                    out.println("ba");
                } else {
                    out.println("NO");
                }
            } else {
                if (s.equals("a")) {
                    out.println("b");
                } else {
                    out.println("NO");
                }
            }
            out.close();
            return;
        }

        for (int i = n - 1; i >= 0; i--) {
            char ch = s.charAt(i);
            for (char ch2 = (char) (ch + 1); ch2 < 'a' + p; ch2++) {
                if (i > 0 && ch2 == s.charAt(i - 1)) {
                    continue;
                }
                if (i > 1 && ch2 == s.charAt(i - 2)) {
                    continue;
                }
                StringBuilder ans = new StringBuilder(s.substring(0, i)).append(ch2);
                for (int j = i + 1; j < n; j++) {
                    char ch3 = 'a';
                    while ((j > 0 && ans.charAt(j - 1) == ch3) || (j > 1 && ans.charAt(j - 2) == ch3)) {
                        ch3++;
                    }
                    ans.append(ch3);
                }
                out.println(ans.toString());
                out.close();
                return;

            }
        }

        out.println("NO");


//        out.println(System.currentTimeMillis() - start);
        out.close();
    }


    private static void outputArray(int[] ans, PrintWriter out) {
        StringBuilder str = new StringBuilder("? ");
        for (long an : ans) {
            str.append(an).append(' ');
        }
        out.println(str);
        out.flush();
    }

    private static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 1024);
            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 String nextString() {
            try {
                return reader.readLine();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

        public long nextLong() {
            return Long.parseLong(next());
        }

        public char nextChar() {
            return next().charAt(0);
        }

        public String nextWord() {
            return next();
        }
    }
}