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

public class Main {
    static boolean isMultiTest = false;

    public static void main(String[] args) {
        OutputStream outputStream = System.out;
        InputStream inputStream = System.in;
        InputFast in = new InputFast();
        PrintWriter out = new PrintWriter(outputStream);
        Task solver = new Task();
        if (isMultiTest) {
            int testNumber = in.nextInt();
            for (int i = 1; i <= testNumber; i++) {
                solver.solve(i, in, out);
            }
        } else {
            solver.solve(1, in, out);
        }
        out.close();
    }
}

class Task {
    final static int MOD = 1000 * 1000 * 1000 + 7;

    public void solve(int testNumber, InputFast in, PrintWriter out) {
        int n = in.nextInt();
        int p = in.nextInt();
        char[] s = in.next(n);
        boolean has = false;
        int pos = -1;
        for (int i = n - 1; i >= 0; --i) {
            boolean flag = false;
            for (char c = (char) (s[i] + 1); c < 'a' + p; c++) {
                char l1 = '.';
                char l2 = '.';
                char r1 = '.';
                char r2 = '.';
                if (i - 1 >= 0) {
                    r1 = s[i - 1];
                }
                if (i - 2 >= 0) {
                    r2 = s[i - 2];
                }
                if (ok(c, l1, l2, r1, r2)) {
                    pos = i;
                    flag = true;
                    has = true;
                    s[i] = c;
                    break;
                }
            }
            if (flag)
                break;
        }
        if (!has) {
            out.println("NO");
            return;
        }

        for (int i = pos + 1; i < n; ++i) {
            for (char c = 'a'; c <= 'a' + p; c++) {
                if (i - 2 >= 0) {
                    if (ok(c, s[i - 1], s[i - 2])) {
                        s[i] = c;
                        break;
                    }
                } else if (i - 1 >= 0) {
                    if (ok(c, s[i - 1])) {
                        s[i] = c;
                        break;
                    }
                }
            }
        }
        String ans = new String(s);
        out.println(ans);
    }

    boolean ok(char c, char... o) {
        for (char i : o) {
            if (c == i)
                return false;
        }
        return true;
    }
}

class InputFast {
    static InputStream is = System.in;
    static private byte[] buffer = new byte[1024];
    static private int lenbuf = 0, ptrbuf = 0;

    private int readByte() {
        if (lenbuf == -1)
            throw new InputMismatchException();
        if (ptrbuf >= lenbuf) {
            ptrbuf = 0;
            try {
                lenbuf = is.read(buffer);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (lenbuf <= 0)
                return -1;
        }
        return buffer[ptrbuf++];
    }

    private boolean isSpace(int c) {
        return !(c >= 33 && c <= 126);
    }

    private int read() {
        int b;
        while ((b = readByte()) != -1 && isSpace(b))
            ;
        return b;
    }

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

    public char nextChar() {
        return (char) read();
    }

    public String next() {
        int b = read();
        StringBuilder sb = new StringBuilder();
        while (!(isSpace(b))) {
            sb.appendCodePoint(b);
            b = readByte();
        }
        return sb.toString();
    }

    public char[] next(int n) {
        char[] buf = new char[n];
        int b = read(), p = 0;
        while (p < n && !(isSpace(b))) {
            buf[p++] = (char) b;
            b = readByte();
        }
        return n == p ? buf : Arrays.copyOf(buf, p);
    }

    public int nextInt() {
        int num = 0, b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
            ;
        if (b == '-') {
            minus = true;
            b = readByte();
        }

        while (true) {
            if (b >= '0' && b <= '9') {
                num = num * 10 + (b - '0');
            } else {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }

    public long nextLong() {
        long num = 0;
        int b;
        boolean minus = false;
        while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
            ;
        if (b == '-') {
            minus = true;
            b = readByte();
        }

        while (true) {
            if (b >= '0' && b <= '9') {
                num = num * 10 + (b - '0');
            } else {
                return minus ? -num : num;
            }
            b = readByte();
        }
    }

}

class Input {
    public BufferedReader reader;
    public StringTokenizer tokenizer;

    public Input(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
        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 nextLine() {
        String s = "";
        try {
            s = reader.readLine();
        } catch (IOException e) {
            try {
                throw new IOException();
            } catch (IOException e1) {
                e1.printStackTrace();
            }
        }
        return s;
    }

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

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

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