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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.FilterInputStream;
import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.File;
import java.io.InputStream;

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

    static class ProblemANoToPalindromes {
        int n;
        int p;
        int[] a;
        Boolean[][][][] memo;
        PrintWriter out;

        boolean dp(int ind, int prev2, int prev, boolean bounded) {
            if (ind == n) return !bounded;
            if (memo[bounded ? 1 : 0][prev2][prev][ind] != null) return memo[bounded ? 1 : 0][prev2][prev][ind];
            int start = bounded ? a[ind] : 1;
            for (int i = start; i <= p; ++i) {
                if (i == prev2 || i == prev) continue;
                if (dp(ind + 1, prev, i, bounded && i == start)) return memo[bounded ? 1 : 0][prev2][prev][ind] = true;
            }
            return memo[bounded ? 1 : 0][prev2][prev][ind] = false;
        }

        void bt(int ind, int prev2, int prev, boolean bounded) {
            if (ind == n) {
                out.println();
                return;
            }
            int start = bounded ? a[ind] : 1;
            for (int i = start; i <= p; ++i) {
                if (i == prev2 || i == prev) continue;
                if (dp(ind + 1, prev, i, bounded && i == start)) {
                    out.print((char) (i + 'a' - 1));
                    bt(ind + 1, prev, i, bounded && i == start);
                    return;
                }
            }
        }

        public void solve(int testNumber, JoltyScanner in, PrintWriter out) {
            this.out = out;
            n = in.nextInt();
            p = in.nextInt();
            a = new int[n];
            memo = new Boolean[2][27][27][n];
            char[] s = in.next().toCharArray();
            for (int i = 0; i < n; ++i) a[i] = s[i] - 'a' + 1;
            if (!dp(0, 0, 0, true)) {
                out.println("NO");
                return;
            }
            bt(0, 0, 0, true);
        }

    }

    static class JoltyScanner {
        public int BS = 1 << 16;
        public char NC = (char) 0;
        public byte[] buf = new byte[BS];
        public int bId = 0;
        public int size = 0;
        public char c = NC;
        public double num = 1;
        public BufferedInputStream in;

        public JoltyScanner(InputStream is) {
            in = new BufferedInputStream(is, BS);
        }

        public JoltyScanner(String s) throws FileNotFoundException {
            in = new BufferedInputStream(new FileInputStream(new File(s)), BS);
        }

        public char nextChar() {
            while (bId == size) {
                try {
                    size = in.read(buf);
                } catch (Exception e) {
                    return NC;
                }
                if (size == -1) return NC;
                bId = 0;
            }
            return (char) buf[bId++];
        }

        public int nextInt() {
            return (int) nextLong();
        }

        public long nextLong() {
            num = 1;
            boolean neg = false;
            if (c == NC) c = nextChar();
            for (; (c < '0' || c > '9'); c = nextChar()) {
                if (c == '-') neg = true;
            }
            long res = 0;
            for (; c >= '0' && c <= '9'; c = nextChar()) {
                res = (res << 3) + (res << 1) + c - '0';
                num *= 10;
            }
            return neg ? -res : res;
        }

        public String next() {
            StringBuilder res = new StringBuilder();
            while (c <= 32) c = nextChar();
            while (c > 32) {
                res.append(c);
                c = nextChar();
            }
            return res.toString();
        }

    }
}

