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.text.DecimalFormat;
import java.util.*;
import java.io.*;
import java.math.*;
public class Main {
	public static long mod= (long) (1e9 +7);
	static InputReader s;
	static PrintWriter out;
	public static void main(String args[]) {
		new Thread(null, new Runnable() {
			public void run() {
				try{
					solve();
					out.flush();
					out.close();
				}
				catch(Exception e){
					e.printStackTrace();
				}
			}
		}, "1", 1 << 26).start();
	}
	public static void solve() throws IOException{
		s= new InputReader(System.in);
		OutputStream outputStream= System.out;
		out= new PrintWriter(outputStream);
		int n= s.nextInt();
		int p= s.nextInt();
		char st[]= new char[n];
		String str= s.next();
		for(int i=0;i<n;i++){
			st[i]= str.charAt(i);
		}
		int i;
		boolean fl=false;
		for(i=n-1;i>=0 && !fl;i--){
			for(int j= st[i]+1;j<(p+'a') && !fl;j++){
//				System.out.println(i);
				if((i-1)>=0){
					if(st[i-1]!=(char)j){
						if((i-2)>=0){
							if(st[i-2]!=(char)j){
								st[i]= (char)j;
								fl=true;
							}
						}
						else{
							st[i]= (char)j;
							fl=true;
						}
					}
				}
				else{
					st[i]= (char)j;
					fl=true;
				}
			}
		}
		if(!fl){
			System.out.println("NO");
			return;
		}
		fl=false;
		int z=i+1;
//		debug(st);
		for(i=z+1;i<n;i++){
			fl=false;
			for(int j='a';j<(p+'a') && !fl;j++){
				if((i-1)>=0){
					if(st[i-1]!=(char)j){
						if((i-2)>=0){
							if(st[i-2]!=(char)j){
								st[i]= (char)j;
								fl=true;
							}
						}
						else{
							st[i]= (char)j;
							fl=true;
						}
					}
				}
				else{
					st[i]= (char)j;
					fl=true;
				}
			}
			if(!fl){
				System.out.println("NO");
				return;
			}
		}
		for(int j=0;j<n;j++){
			out.print(st[j]);
		}
	}

	static long modulo(long x,long y,long p)	
	{
		 long res = 1;
		 x = x % p;  
		 
	    while (y > 0)
	    {
	        if (y%2==1)
	            res = (res*x) % p;
	 
	        y = y>>1;
	        x = (x*x) % p;  
	    }
	    return res;
	}
	
	static HashSet<Integer> primeFactors(int n)   // O(sqrt(n))
	{
	    // Print the number of 2s that divide n
		HashSet<Integer> arr= new HashSet<>();
	    while (n%2 == 0)
	    {
	        arr.add(2);
	        n = n/2;
	    }
	 
	    // n must be odd at this point.  So we can skip one element (Note i = i +2)
	    for (int i = 3; i <= Math.sqrt(n); i = i+2)
	    {
	        // While i divides n, print i and divide n
	        while (n%i == 0)
	        {
	            arr.add(i);
	            n = n/i;
	        }
	    }
	    // This condition is to handle the case when n is a prime number
	    // greater than 2
	    if (n > 2)
	        arr.add(n);
	    
	    return arr;
	}
 
	public static long expo(long a, long b){
		if (b==0)
	        return 1;
	    if (b==1)
	        return a;
	    if (b==2)
	        return a*a;
 
	    if (b%2==0){
	            return expo(expo(a,(b/2)),2);
	    }
	    else{
	        return a*expo(expo(a,(b-1)/2),2);
	    }
	}
	static class Pair implements Comparable<Pair>
	{
		int a;
		int b;
//		int c;
		Pair(int aa, int bb)
		{
			a= aa;
			b= bb;
//			c=cc;
		}
		
		public int compareTo(Pair o) 
		{
			int ans = Integer.compare(this.a,o.a);
			return ans;
//			return ans==0 ? -Integer.compare(this.b, o.b):ans;
//			if(Long.compare(this.x, o.x)!=0)
//				return -Long.compare(this.x, o.x);
//			else
//				return Long.compare(this.y, o.y);
//			return Integer.compare(this.x, o.x);
	//		return Long.compare(this.x, o.x);
		}
		
		public int hashCode() {
			int hu = (int) (a ^ (a >>> 32));
			int hv = (int) (b ^ (b >>> 32));
			return 31 * hu + hv;
		}
// 
		public boolean equals(Object o) {
			Pair other = (Pair) o;
			return a == other.a && b == other.b;
		}
		
		public String toString() {
			return "[x=" + a + ", y=" + b + "]";
		}
		
	}
	
	public static int[] sieve(int N){    // O(n*log(logn))
		int arr[]= new int[N+1];
		for(int i=2;i<=Math.sqrt(N);i++){
			if(arr[i]==0){
				for(int j= i*i;j<= N;j= j+i){
					arr[j]=1;
				}
			}
		}
		return arr;
		// All the i for which arr[i]==0 are prime numbers.
	}
	static int gcd(int a,int b){       // O(logn)
		if(b==0) return a;
		return gcd(b,a%b);
	}
	
	public static void debug(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}
	
	static void catalan_numbers(int n) {
		long catalan[]= new long[n+1];
	    catalan[1] = 1;
	    for (int i = 2; i <= n; i++) {
	        for (int j = 1; j <= i - 1; j++) {
	            catalan[i] = catalan[i] + ((catalan[j]) * catalan[i - j]);
	        }
	    }
	}
	
	static final class InputReader{
        private final InputStream stream;
        private final byte[] buf=new byte[1024];
        private int curChar;
        private int Chars;
        public InputReader(InputStream stream){this.stream=stream;}
		private int read()throws IOException{
            if(curChar>=Chars){
                curChar=0;
                Chars=stream.read(buf);
                if(Chars<=0)
                    return -1;
            }
            return buf[curChar++];
        }
        public final int nextInt()throws IOException{return (int)nextLong();}
        public final long nextLong()throws IOException{
            int c=read();
            while(isSpaceChar(c)){
                c=read();
                if(c==-1) throw new IOException();
            }
            boolean negative=false;
            if(c=='-'){
                negative=true;
                c=read();
            }
            long res=0;
            do{
                if(c<'0'||c>'9')throw new InputMismatchException();
                res*=10;
                res+=(c-'0');
                c=read();
            }while(!isSpaceChar(c));
            return negative?(-res):(res);
        }
        public final int[] nextIntBrray(int size)throws IOException{
            int[] arr=new int[size];
            for(int i=0;i<size;i++)arr[i]=nextInt();
            return arr;
        }
        public final String next()throws IOException{
            int c=read();
            while(isSpaceChar(c))c=read();
            StringBuilder res=new StringBuilder();
            do{
                res.append((char)c);
                c=read();
            }while(!isSpaceChar(c));
            return res.toString();
        }
        public final String nextLine()throws IOException{
            int c=read();
            while(isSpaceChar(c))c=read();
            StringBuilder res=new StringBuilder();
            do{
                res.append((char)c);
                c=read();
            }while(c!='\n'&&c!=-1);
            return res.toString();
        }
        private boolean isSpaceChar(int c){
            return c==' '||c=='\n'||c=='\r'||c=='\t'||c==-1;
        }
    }
}