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.util.*;
import java.math.*;
import java.math.BigInteger; 
//import javafx.util.*; 
public final class B
{    
	static PrintWriter out = new PrintWriter(System.out); 
	static StringBuilder ans=new StringBuilder();
	static FastReader in=new FastReader();
	static ArrayList<Integer> g[];
	static long mod=(long)(1e9+7);
	static int D1[],D2[],par[];
	static boolean set[];
	static int value[];
	static long INF=Long.MAX_VALUE;
	static int val[],tot[],max[];
	static int min;
	static int dp[][];
	static int path[][],A[];
	static char X[][];
	static int index[];
	public static void main(String args[])throws IOException
	{

		int N=i(),P=i();
		char X[]=in.next().toCharArray();
		for(int i=N-1; i>=0; i--)
		{
			for(int x=(X[i]-'a')+1; x<P; x++)
			{
				char c=(char)(x+'a');
				char a='#',b='#';
				if(i-1>=0)a=X[i-1];
				if(i-2>=0)b=X[i-2];
				if(c!=a && c!=b)
				{
//					System.out.println("runnning--> "+" i--> "+ i+" "+a+ " "+b+" "+c);
					//we can place X[i]=c;
					X[i]=c;
//					print(X);
					boolean f=true;
					for(int j=i+1; j<N; j++)
					{
						f=false;
						for(int y='a'; y<'a'+P; y++)
						{
							a='#';
							b='#';
							char ch=(char)y;
							if(j-1>=0)a=X[j-1];
							if(j-2>=0)b=X[j-2];
							if(a!=ch && b!=ch)
							{
								//if this does not happen f=false;
//								System.out.println(a+" "+b+" ch--> "+ch);
								X[j]=ch;
								f=true;
								break;
							}
						}
						if(!f)break;						
					}
					if(f)
					{
						for(char z:X)ans.append(z);
						System.out.println(ans);
						return;
					}
					
				}
				
			}
		
		}
//		print(X);
		System.out.println("NO");
		
	}
	static int f(int x,int y,int i,int A[],int B[])
	{
		//		System.out.println("x--> "+x+" y--> "+y+" i--> "+i);
		if(i==A.length)
		{
			if(x>=y)return x;
			return Integer.MAX_VALUE;
		}
		if(dp[x][y]==-1)
		{
			dp[x][y]=Math.min(f(x+A[i],y,i+1,A,B),f(x,y+B[i],i+1,A,B));
		}
		return dp[x][y];
	}
	static int or(int i,int j)
	{
		System.out.println("OR "+i+" ");
		return i();
	}
	static int and(int i,int j)
	{
		System.out.println("AND "+i+" "+j);
		return i();
	}
	static int xor(int i,int j)
	{
		System.out.println("XOR "+i+" "+j);
		return i();
	}
	static String f(char X[],int d,int K)
	{
		StringBuilder sb=new StringBuilder();
		StringBuilder s=new StringBuilder();
		int x=K/d;
		String Y="";
		for(int i=0; i<d; i++)s.append(X[i]);
		Y=s.toString();
		while(x-->0)
			sb.append(Y);
		x=K%d;
		for(int i=0; i<x; i++)sb.append(X[i]);
		return sb.toString();	
	}
	static long f(long t,long x,long N,long v)
	{
		long l=0,r=N+1;
		while(r-l>1)
		{
			long m=(l+r)/2;
			if(t+m*x<=N*x)l=m;
			else r=m;
		}
		return l;
	}

	static void f(int dp[][],int d,int A[],int par[])
	{
		if(A[d]==0)return ;
		f(dp,d+1,A,par);
		dp[0][d]=A[d]+Math.min(dp[0][d+1], dp[1][d+1]);
		if(dp[0][d+1]<dp[1][d+1])
		{
			par[d]=1;
		}
		else par[d]=2;
		dp[1][d]=dp[0][d+1];

	}
	static int [] ask(int a,int N)
	{
		System.out.println("? "+a);
		int A[]=input(N);
		return A;
	}
	static boolean isPalin(char X[])
	{
		int l=0,r=X.length-1;
		while(l<=r)
		{
			if(X[l]!=X[r])return false;
			l++;
			r--;
		}
		return true;
	}

	static boolean isSorted(int A[])
	{
		int N=A.length;
		for(int i=0; i<N-1; i++)
		{
			if(A[i]>A[i+1])return false;
		}

		return true;		
	}
	static int f1(int x,ArrayList<Integer> A)
	{
		int l=-1,r=A.size();
		while(r-l>1)
		{
			int m=(l+r)/2;
			int a=A.get(m);
			if(a<x)l=m;
			else r=m;
		}		
		return l;
	}






	static int max(int a,int b,int c)
	{
		return Math.max(a, Math.max(c, b));
	}
	static int value(char X[],char Y[])
	{
		int c=0;
		for(int i=0; i<7; i++)
		{
			if(Y[i]=='1' && X[i]=='0')return -1;
			if(X[i]=='1' && Y[i]=='0')c++;
		}
		return c;
	}
	//	static boolean isValid(int i,int j)
	//	{
	//		if(i<0 || i>=N)return false;
	//		if(j<0 || j>=M)return false;
	//		return true;
	//	}

	static long fact(long N)
	{
		long num=1L;
		while(N>=1)
		{
			num=((num%mod)*(N%mod))%mod;
			N--;
		}
		return num;
	}
	static boolean reverse(long A[],int l,int r)
	{
		while(l<r)
		{
			long t=A[l];
			A[l]=A[r];
			A[r]=t;
			l++;
			r--;
		}
		if(isSorted(A))return true;
		else return false;
	}
	static boolean isSorted(long A[])
	{
		for(int i=1; i<A.length; i++)if(A[i]<A[i-1])return false;
		return true;
	}
	static boolean isPalindrome(char X[],int l,int r)
	{
		while(l<r)
		{
			if(X[l]!=X[r])return false;
			l++; r--;
		}
		return true;
	}

	static long min(long a,long b,long c)
	{
		return Math.min(a, Math.min(c, b));
	}

	static void print(int a)
	{
		System.out.println("! "+a);
	}
	static int find(int a)
	{
		if(par[a]<0)return a;
		return par[a]=find(par[a]);
	}
	static void union(int a,int b)
	{
		a=find(a);
		b=find(b);
		if(a!=b)
		{
			par[a]+=par[b]; //transfers the size
			par[b]=a;       //changes the parent
		}
	}
	static void swap(char A[],int a,int b)
	{
		char ch=A[a];
		A[a]=A[b];
		A[b]=ch;
	}

	static void sort(long[] a) //check for long
	{
		ArrayList<Long> l=new ArrayList<>();
		for (long i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	static void setGraph(int N)
	{
		g=new ArrayList[N+1];		
		val=new int[N+1];
		for(int i=0; i<=N; i++)
		{	
			g[i]=new ArrayList<Integer>();
		}
	}

	static  long pow(long a,long b)
	{
		long mod=1000000007;
		long pow=1;
		long x=a;
		while(b!=0)
		{
			if((b&1)!=0)pow=(pow*x)%mod;
			x=(x*x)%mod;
			b/=2;
		}
		return pow;
	}
	static long toggleBits(long x)//one's complement || Toggle bits
	{
		int n=(int)(Math.floor(Math.log(x)/Math.log(2)))+1;

		return ((1<<n)-1)^x;
	}
	static int countBits(long a)
	{
		return (int)(Math.log(a)/Math.log(2)+1);
	}
	static void sort(int[] a) {
		ArrayList<Integer> l=new ArrayList<>();
		for (int i:a) l.add(i);
		Collections.sort(l);
		for (int i=0; i<a.length; i++) a[i]=l.get(i);
	}
	static boolean isPrime(long N)
	{
		if (N<=1)  return false; 
		if (N<=3)  return true; 
		if (N%2 == 0 || N%3 == 0) return false; 
		for (int i=5; i*i<=N; i=i+6) 
			if (N%i == 0 || N%(i+2) == 0) 
				return false; 
		return true; 
	}
	static long GCD(long a,long b) 
	{
		if(b==0)
		{
			return a;
		}
		else return GCD(b,a%b );
	}

	//Debugging Functions Starts

	static void print(char A[])
	{
		for(char c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(boolean A[])
	{
		for(boolean c:A)System.out.print(c+" ");
		System.out.println();
	}
	static void print(int A[])
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();	
	}
	static void print(long A[])
	{
		for(long i:A)System.out.print(i+ " ");
		System.out.println();

	}
	static void print(ArrayList<Integer> A)
	{
		for(int a:A)System.out.print(a+" ");
		System.out.println();
	}

	//Debugging Functions END
	//----------------------
	//IO FUNCTIONS STARTS
	static HashMap<Integer,Integer> Hash(int A[])
	{
		HashMap<Integer,Integer> mp=new HashMap<>();
		for(int a:A)
		{
			int f=mp.getOrDefault(a,0)+1;
			mp.put(a, f);
		}
		return mp;
	}
	static int i()
	{
		return in.nextInt();
	}

	static long l()
	{
		return in.nextLong();
	}

	static int[] input(int N){
		int A[]=new int[N];
		for(int i=0; i<N; i++)
		{
			A[i]=in.nextInt();
		}
		return A;
	}

	static long[] inputLong(int N)     {
		long A[]=new long[N];
		for(int i=0; i<A.length; i++)A[i]=in.nextLong();
		return A;
	}

	//IO FUNCTIONS END

}

class node implements Comparable<node>
{
	int par,a;
	node(int par,int a)
	{
		this.par=par;
		this.a=a;
	}
	public int compareTo(node x)
	{
		return this.par-x.par;
	}
}

//Code For FastReader
//Code For FastReader
//Code For FastReader
//Code For FastReader
class FastReader
{
	BufferedReader br;
	StringTokenizer st;
	public FastReader()
	{
		br=new BufferedReader(new InputStreamReader(System.in));
	}

	String next()
	{
		while(st==null || !st.hasMoreElements())
		{
			try
			{
				st=new StringTokenizer(br.readLine());
			}
			catch(IOException e)
			{
				e.printStackTrace();
			}
		}
		return st.nextToken();
	}

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

	long nextLong()
	{
		return Long.parseLong(next());
	}
	//gey
	double nextDouble()
	{
		return Double.parseDouble(next());
	}

	String nextLine()
	{
		String str="";
		try
		{
			str=br.readLine();
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
		return str;
	}

}