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.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.HashMap;
import java.util.StringTokenizer;


public class Solution{
	
	///////////////////////////////////////////////////////////////////////////
	static class FastScanner{
		BufferedReader s;
		StringTokenizer st;
		
		public FastScanner(){
			st = new StringTokenizer("");
			s = new BufferedReader(new InputStreamReader(System.in));
		}
		
		public FastScanner(File f) throws FileNotFoundException{
			st = new StringTokenizer("");
			s = new BufferedReader (new FileReader(f));
		}
		
		public int nextInt() throws IOException{
			if(st.hasMoreTokens())
				return Integer.parseInt(st.nextToken());
			else{
				st = new StringTokenizer(s.readLine());
				return nextInt();
			}
		}
		
		public double nextDouble() throws IOException{
			if(st.hasMoreTokens())
				return Double.parseDouble(st.nextToken());
			else{
				st = new StringTokenizer(s.readLine());
				return nextDouble();
			}
		}
		
		public long nextLong() throws IOException{
			if(st.hasMoreTokens())
				return Long.parseLong(st.nextToken());
			else{
				st = new StringTokenizer(s.readLine());
				return nextLong();
			}
		}
		
		public String nextString() throws IOException{
			if(st.hasMoreTokens())
				return st.nextToken();
			else{
				st = new StringTokenizer(s.readLine());
				return nextString();
			}
			
		}
		public String readLine() throws IOException{
			return s.readLine();
		}
		
		public void close() throws IOException{
			s.close();
		}
		
	}
	
	////////////////////////////////////////////////////////////////////
	//		Number Theory
	
	long pow(long a,long b,long mod){
		long x = 1; long y = a;
		while(b > 0){
			if(b % 2 == 1){
				x = (x*y);
				x %= mod;
			}
			y = (y*y);
			y %= mod;
			b /= 2;			
		}
		return x;
	}
	
	int divisor(long x,long[] a){
	    long limit = x;
	    int numberOfDivisors = 0;

	    for (int i=1; i < limit; ++i) {
	        if (x % i == 0) {
	            limit = x / i;
	            if (limit != i) {
	                numberOfDivisors++;
	            }
	            numberOfDivisors++;
	        }
	    }
	    return numberOfDivisors;
    }
	
	void findSubsets(int array[]){
    	
	    long numOfSubsets = 1 << array.length; 
	    for(int i = 0; i < numOfSubsets; i++){
	    		
	    	int pos = array.length - 1;
	    	int bitmask = i;

	    	while(bitmask > 0){		
	    		if((bitmask & 1) == 1)
	   				ww.print(array[pos]+" ");
	   			bitmask >>= 1;
	        	pos--;
	    	}

	    	ww.println();
	   	}
	}
    
	
	public static int gcd(int a, int b){
		return b == 0 ? a : gcd(b,a%b);
	}
	
  
	public static int lcm(int a,int b, int c){
		return lcm(lcm(a,b),c);
	}
	
	public static int lcm(int a, int b){
		return a*b/gcd(a,b);
	}
	
	
	////////////////////////////////////////////////////////////////////
	
	
//	  private static  	FastScanner s = new FastScanner(new File("input.txt"));
//	  private static PrintWriter ww = new PrintWriter(new FileWriter("output.txt"));
	  private static FastScanner s = new FastScanner();   
      private static PrintWriter ww = new PrintWriter(new OutputStreamWriter(System.out));
//      private static Scanner s = new Scanner(System.in);
	@SuppressWarnings("unused")
	private static int[][] states = { {-1,0} , {1,0} , {0,-1} , {0,1} };
	
      
    //////////////////////////////////////////////////////////////////// 
      
     
    public static void main(String[] args) throws IOException{
 		new Solution().solve();
 	}
    
    ////////////////////////////////////////////////////////////////////
    
    int n;
    int p;
    char[] arr;
    char[] ans;
    
    boolean dfs(int i, boolean set){
    	
    	if(i == n) return true;
    	boolean status = false;
    	
    	for(char c = set ? 'a' : arr[i] ; c - 'a' < p ; c++){
    		
    		ans[i] = c;
    		if(i > 0 && ans[i] == ans[i-1]) continue;
    		if(i > 1 && ans[i] == ans[i-2]) continue;
    		status = dfs(i+1,set);
    		if(status){
    			return true;
    		}
    		set = true;
    	}
    	return false;
    }
    
	void solve() throws IOException{
		
		n = s.nextInt();
		p = s.nextInt();
		arr = s.nextString().toCharArray();
		ans = new char[n];
		
		arr[n-1]++;
		if(dfs(0,false)){
			for(int i=0;i<n;i++)
				ww.print(ans[i]);
			ww.println();
		}else ww.println("NO");
		
        s.close();
 	    ww.close(); 
     }
    
}