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.
from __future__ import division, print_function

import os
import sys
from io import BytesIO, IOBase

def main():
    def getAvailableStart():
        for i in range(n-1, -1, -1):
            originalCharId = ord(string[i]) - 97

            for charId in range(originalCharId + 1, p):
                newChar = chr(charId + 97)

                if i == 0:
                    return i, newChar

                if i >= 1:
                    if newChar == string[i-1]: continue
                if i >= 2:
                    if newChar == string[i-2]: continue

                return i, newChar

        return -1, ''

    n, p = [ int(x) for x in input().split() ]
    string = input()

    if (n <= 3 and p < n) or (n > 3 and p < 3):
        print('NO')
        return

    start, newChar = getAvailableStart()

    if ~start:
        stringAsArray = [ char for char in string ]
        stringAsArray[start] = newChar

        bestChars = ['a', 'b', 'c']

        for i in range(start + 1, n):
            for char in bestChars:
                if i >= 1:
                    if char == stringAsArray[i-1]: continue
                if i >= 2:
                    if char == stringAsArray[i-2]: continue

                break

            stringAsArray[i] = char

        print(''.join(stringAsArray))

    else:
        print('NO')


BUFFSIZE = 8192

class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)

class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")

input = lambda: sys.stdin.readline().rstrip("\r\n")

def print(*args, **kwargs):
    sep = kwargs.pop("sep", " ")
    file = kwargs.pop("file", sys.stdout)

    atStart = True
    for x in args:
        if not atStart:
            file.write(sep)
        file.write(str(x))
        atStart = False
    file.write(kwargs.pop("end", "\n"))

    if kwargs.pop("flush", False):
        file.flush()

sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)

main()
