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.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.io.PrintWriter;
import static java.lang.Math.abs;
import static java.lang.Math.max;
import static java.lang.Math.min;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import static java.util.Arrays.fill;
import java.util.Collections;
import java.util.Locale;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;



//<editor-fold defaultstate="collapsed" desc="Main">
public class Solution {
// https://netbeans.org/kb/73/java/editor-codereference_ru.html#display
    private void run() {
        try {
            Locale.setDefault(Locale.US);
        } catch (Exception e) {
        }
        boolean oj = true;
        try {
            oj = System.getProperty("MYLOCAL") == null;
        } catch (Exception e) {
        }

        if (oj) {
            sc = new FastScanner(new InputStreamReader(System.in));
            out = new PrintWriter(new OutputStreamWriter(System.out));
        } else {
            try {
                sc = new FastScanner(new FileReader("input.txt"));
                out = new PrintWriter(new FileWriter("output.txt"));
            } catch (IOException e) {
                MLE();
            }
        }
        Solver s = new Solver();
        s.sc = sc;
        s.out = out;
        s.solve();
        if (!oj) {
            err.println("Time: " + (System.currentTimeMillis() - timeBegin) / 1e3);
            err.printf("Mem: %d\n", (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()) >> 20);
        }
        out.flush();
    }

    private void show(int[] arr) {
        for (int v : arr) {
            err.print(" " + v);
        }
        err.println();
    }

    public static void exit() {
        err.println("Time: " + (System.currentTimeMillis() - timeBegin) / 1e3);
        out.flush();
        out.close();
        System.exit(0);
    }

    public static void MLE() {
        int[][] arr = new int[1024 * 1024][];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = new int[1024 * 1024];
        }
    }

    public static void main(String[] args) {
        new Solution().run();
    }

    static long timeBegin = System.currentTimeMillis();
    static FastScanner sc;
    static PrintWriter out;
    static PrintStream err = System.err;
}
//</editor-fold>

//<editor-fold defaultstate="collapsed" desc="FastScanner">
class FastScanner {

    BufferedReader br;
    StringTokenizer st;

    FastScanner(InputStreamReader reader) {
        br = new BufferedReader(reader);
        st = new StringTokenizer("");
    }

    String next() {
        while (!st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException ex) {
                Solution.MLE();
            }
        }
        return st.nextToken();
    }

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

    long nextLong() {
        return Long.parseLong(next());
    }
    double nextDouble() {
        return Double.parseDouble(next());
    }
}
//</editor-fold>

final class Slider{
    int l, r;
    long[] arr;
    ArrayDeque<Long> Q;

    public Slider(int l, int r, long[] arr) {
        this.l = l;
        this.r = r;
        this.arr = arr;
        Q = new ArrayDeque<>();
        for( int i = max(l,1); i <= min(arr.length-1,r); ++i ){
            add( arr[i] );
        }
    }
    
    void add( long val ){
        while( !Q.isEmpty() && Q.getLast() < val )
            Q.removeLast();
        Q.add(val);
    }
    
    void next(){
        if( 1 <= l && l < arr.length && Q.getFirst() == arr[l] )
            Q.removeFirst();
        ++l;
        //
        if( 1 <= r+1 && r+1 < arr.length  )
            add( arr[r+1] );
        ++r;
    }
    
    long getMax(){
//        long max = Long.MIN_VALUE;
//        for( int i = max(l,1); i <= min(arr.length-1,r); ++i )
//            max = max( max, arr[i] );
//        if( max != Q.getFirst() ) 
//            Solution.MLE();
        return Q.getFirst();
    }
}

class Pair{
    int a, b;

    public Pair(int a, int b) {
        this.a = a;
        this.b = b;
    }
}

class Solver {
    void ass(boolean OK) { if(!OK)Solution.MLE(); }
    FastScanner sc;
    PrintWriter out;
    static PrintStream err = System.err;

    int n, p;
    char[] str;

    boolean set( int i, char beg ){
        for( char ch = beg; ch <= 'a' + p - 1; ++ch ){
            if( ( i-1 < 0 || ch != str[i-1]) &&
                ( i-2 < 0 || ch != str[i-2]) ){
                str[i] = ch;
                return true;
            }
        }
        return false;
    }
    
    void solve() {
        n = sc.nextInt();
        p = sc.nextInt();
        str = sc.next().toCharArray();
        for( int i = str.length-1; 0 <= i; --i ){
            if( set(i,(char)(str[i]+1)) ){
                err.println(i);
                for (int j = i + 1; j < str.length; j++) {
                    set(j,'a');
                }
                out.println(new String(str));
                return;
            }
        }
        out.println("NO");
    }
    
}