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.*;
import java.util.*;
public class Main {

    public static void main(String[] args) 
    {	
        InputStream inputstream = System.in;
        OutputStream outputstream = System.out;
        InputReader in = new InputReader(inputstream);
        OutputWriter out = new OutputWriter(outputstream);
        mysolver mysol = new mysolver();
        mysol.solve(in, out);
        out.close();
    }

}
class node implements Comparable<node>{
	int count;
	long value;
	public int compareTo(node t)
	{
		if(this.value == t.value)
			return 0;
		else if(this.value < t.value)
			return -1;
		else
			return 1;
	}
}
class mysolver {
	public long mod = 1000000007;
    public void solve(InputReader in,OutputWriter out)
    {
    	PrintWriter pout = new PrintWriter(new BufferedOutputStream(System.out));	
    	int n = in.readInt();
    	int p = in.readInt();
    	String str = in.readString();
    	char[] ch = str.toCharArray();
    	int length = ch.length;
    	int ans = 0;
    	int idx = largestidx(ch,p);
    	
    	if(idx == Integer.MAX_VALUE)
    	{
    		System.out.println("NO");
    		return;
    	}
    	for(int i=idx;i<length;i++)
    	{
    		
    		if(ans == 1)
    		{
    		//	System.out.println(i);
    			int check = 0;
    			check = 0;
    			for(int j=97;j<97+p;j++)
    			{
    				check = 0;
    			//	System.out.println(j+" j "+check);
    				if(i-1>=0)
        			{
        				if((char)j == ch[i-1])
        				{
        				//	System.out.println(j+"++");
        					check = 1;
        				}
        			}
        			if(i-2>=0)
        			{
        				if((char)j == ch[i-2])
        				{
        				//	System.out.println(j+"++");
        					check = 1;
        				}
        			}
        			if(check == 0)
        			{
        			//	System.out.println("YO");
        				ch[i] = (char)j;
        				break;
        			}
    			}
    			//continue;
    		}
    		else
    		{
    			//System.out.println("YO "+(int)ch[i]);
	    		int check = 0;
	    		int no  = -1;
	    		for(int j = ch[i]+1;j<97+p;j++)
	    		{//System.out.println(j+" LLLddd");
	    			check = 0;
	    			if(i-1>=0)
	    			{
	    				if(j==ch[i-1])
	    				{
	    					//System.out.println(j+" LLLddd");
	    					check = 1;
	    				}
	    			}
	    			if(i-2>=0)
	    			{
	    				if(j==ch[i-2])
	    				{
	    					//System.out.println(j+" LLLwwd");
	    					check = 1;
	    				}
	    			}
	    			if(check == 0)
	    			{
	    				//System.out.println(j+" LLL");
	    				ch[i] = (char)j;
	    				ans = 1;
	    				break;
	    			}
	    		}
    		}
    	}
    	if(ans == 0)
    	{
    		pout.println("NO");
    	}
    	else
    	{
    		pout.println(ch);
    	}
        pout.close();
    }
    public int largestidx(char[] ch,int p)
    {
    	int length = ch.length;
    	int largest = Integer.MAX_VALUE;
    	for(int i=0;i<length;i++)
    	{
    		int check = 0;
    		for(int j=ch[i]+1;j<97+p;j++)
    		{
    			check = 0;
    			if(i-1>=0)
    			{
    				if(ch[i-1]==j)
    					check = 1;
    			}
    			if(i-2>=0)
    			{
    				if(ch[i-2]==j)
    					check = 1;
    			}
    			if(check ==0 )
    			{
    				largest = i;
    				break;
    			}
    		}
    	}
    	return largest;
    }
}
class InputReader {
    private InputStream stream;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
    private SpaceCharFilter filter;
 
    public InputReader(InputStream stream) {
        this.stream = stream;
    }
    
    public int read() {
        if (numChars == -1)
            throw new InputMismatchException();
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }
 
    public int readInt() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9')
                throw new InputMismatchException();
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }
 
    public String readString() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do {
            res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }
 
    public boolean isSpaceChar(int c) {
        if (filter != null)
            return filter.isSpaceChar(c);
        return isWhitespace(c);
    }
 
    public static boolean isWhitespace(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }
 
    public String next() {
        return readString();
    }
 
    public interface SpaceCharFilter {
        public boolean isSpaceChar(int ch);
    }
}
 
class OutputWriter {
    private final PrintWriter writer;
 
    public OutputWriter(OutputStream outputStream) {
        writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
    }
 
    public OutputWriter(Writer writer) {
        this.writer = new PrintWriter(writer);
    }
 
    public void close() {
        writer.close();
    }
 
    public void printLine(int i) {
        writer.println(i);
    }
}
 
class IOUtils {
 
    public static void readIntArrays(InputReader in, int[]... arrays) {
        for (int i = 0; i < arrays[0].length; i++) {
            for (int j = 0; j < arrays.length; j++)
                arrays[j][i] = in.readInt();
        }
    }
 
    }
