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.lang.reflect.Array; 
import java.math.BigDecimal;
import java.math.BigInteger; 
import java.sql.Time;
import java.util.*; 
import java.util.Map.Entry;

import static java.lang.Math.*; 
   
public class solver implements Runnable { 
        final boolean ONLINE_JUDGE = System.getProperty("ONLINE_JUDGE") != null; 
        BufferedReader in; 
        PrintWriter out; 
        StringTokenizer tok = new StringTokenizer(""); 
        
        boolean HasTokens(){
            while(!tok.hasMoreTokens()){ 
                try{ 
                        tok = new StringTokenizer(in.readLine()); 
                }catch (Exception e){ 
                        return false; 
                } 
            }
            return true;
        }
          
        String readString() throws IOException{                 
            return HasTokens() ? tok.nextToken():null; 
        } 
        String readString(String delim) throws IOException{ 
            return HasTokens() ? tok.nextToken(delim):null;
        } 
         
        int readInt() throws IOException{ 
            return Integer.parseInt(readString()); 
        }   
        long readLong() throws IOException{ 
            return Long.parseLong(readString()); 
        }       
        double readDouble() throws IOException{ 
            return Double.parseDouble(readString()); 
        }  
        char readChar() throws IOException { 
            char val = 0; 
            do{ 
                val = (char) in.read(); 
            }while(val == '\n' || val == '\r'); 
            return val; 
        } 
        char readChar(String skipChars)throws IOException{ 
            char val = 0; 
            boolean ret; 
            do{ 
                val = (char) in.read(); 
                ret = false; 
                for (int i = skipChars.length()-1; i >= 0; i--){ 
                    if (skipChars.charAt(i) == val){ 
                        ret = true; 
                        break; 
                    } 
                } 
            }while(ret); 
            return val; 
        }
//----------------------------------
        int gcd(int x, int y){
            while (y != 0) {
                int temp = x%y; x = y; y = temp;
            }
            return x;
        }
//----------------------------------        
          
        public class Pair<T1,T2> { 
            public T1 x1; 
            public T2 x2; 
            public Pair(){}; 
            public Pair(T1 x1, T2 x2){ 
                this.x1 = x1; 
                this.x2 = x2; 
            } 
            public String toString(){ 
                return x1 + ":" + x2; 
            } 
        } 
        public class Point implements Comparable<Point>{ 
            public int x2; int x1; 
            public Point(){} 
            public Point(int a, int b){x1 = a;x2=b;} 
            public int compareTo(Point o) {
                return (int)-(x1*x2 - o.x1*o.x2); 
                //if (x1 == o.x1) return -(x2 -o.x2);
                //return (x1-o.x1);  
                // (x1-o.x1) - increase; -(x1-o.x1) - decrease 
            } 
            public String toString(){ 
                return x1 + ":" + x2; 
            } 
            @Override
            public int hashCode() {
                final int prime = 31;
                int result = 1;
                result = prime * result + getOuterType().hashCode();
                result = prime * result + x1;
                result = prime * result + x2;
                return result;
            }
            @Override
            public boolean equals(Object obj) {
                if (this == obj)
                    return true;
                if (obj == null)
                    return false;
                if (getClass() != obj.getClass())
                    return false;
                Point other = (Point) obj;
                if (!getOuterType().equals(other.getOuterType()))
                    return false;
                if (x1 != other.x1)
                    return false;
                if (x2 != other.x2)
                    return false;
                return true;
            }
            private solver getOuterType() {
                return solver.this;
            }
        } 
        public class Three implements Comparable<Three>{ 
            public int x1, x2, x3; 
            public Three(){} 
            public Three(int a, int b, int c){x1 = a;x2=b;x3=c;} 
            public int compareTo(Three o) {
                if(x1 == o.x1 && x2 == o.x2) return x3-o.x3;
                if(x1 == o.x1) return x2-o.x2;
                return (x1-o.x1);  
                // (x1-o.x1) - increase; -(x1-o.x1) - decrease 
            } 
            public String toString(){ 
                return x1 + ":" + x2 + ":" + x3; 
            } 
        } 
//----------------------------------------     
        int n, p;
        char[] s;
        char[] tr;
        
        public void solve() throws IOException {        
            
            n = readInt();          
            p = readInt();
            
            s = readString().toCharArray();
            tr = s.clone();
            boolean y = false;
            
            
            for (int i = n-1; i>= 0 && !y; i--){
                for (int j = s[i] - 'a' + 1; j < p; j++){
                    s[i] = (char)(j+'a');
                    if (Can(i) && Set(i+1)){
                        y = true;
                        break;
                    }
                }
            }
            
            
            if (!y){
                out.print("NO");
            }
            else{
                for (char e : s){
                    out.print(e);
                }
            }
        }
        
        boolean Set(int x){
            if (x == n) return true;
            
            for (int i = 0; i < p; i++){
                s[x] = (char)(i + 'a');
                if (Can(x) && Set(x+1)){
                    return true;
                }
            }
            return false;
        }
        
        
        boolean Can(int x){
            if (x-1 >= 0 && s[x-1] == s[x]){
                return false;
            }
            if (x-2 >= 0 && s[x-2] == s[x]){
                return false;
            }
//          if (x+1 < n && s[x+1] == s[x]){
//              return false;
//          }
//          if (x+2 < n && s[x+2] == s[x]){
//              return false;
//          }
            return !false;
        }
        
//---------------------------------------- 
        public static void main(String[] args){ 
                new Thread(null, new solver(), "", 256 * (1L << 20)).start(); 
        } 
         
        public void run(){ 
                try{ 
                        timeBegin = System.currentTimeMillis(); 
                        try{ 
                            if (ONLINE_JUDGE){ 
                                in = new BufferedReader(new InputStreamReader(System.in)); 
                                out = new PrintWriter(System.out); 
                            }  
                            else { 
                                in = new BufferedReader(new FileReader("input.txt")); 
                                out = new PrintWriter("output.txt"); 
                            } 
                        }catch(Throwable e){
                            in = new BufferedReader(new InputStreamReader(System.in)); 
                            out = new PrintWriter(System.out); 
                        }
                          
                        solve(); 
                        out.close(); 
                          
                        timeEnd = System.currentTimeMillis(); 
                        System.err.println("Time = " + (timeEnd - timeBegin)); 
                }catch (Exception e){ 
                        e.printStackTrace(System.err); 
                        System.exit(-1); 
                } 
        } 
         
        long timeBegin, timeEnd; 
   
          
//----------        
        void update(int[] doo, int v, int i, int val, int ll, int rr){ 
            if (ll == rr){ 
                doo[v] = val; 
            }else{ 
                int med = ll + ((rr-ll)>>1); 
                  
                if (i <= med){ 
                    update(doo, v<<1, i, val, ll, med); 
                }else{ 
                    update(doo, (v<<1)+1, i, val, med+1, rr); 
                } 
                doo[v] = min(doo[v<<1], doo[(v<<1)+1]); 
            } 
        } 
        long get(long[] doo, int v, int l, int r, int ll, int rr){ 
            if (l > r){ 
                return Integer.MAX_VALUE; 
            } 
            if (ll == l && r == rr){ 
                return doo[v]; 
            } 
            int med = ll + ((rr-ll)>>1);
            return min(get(doo, v<<1, l, min(r, med), ll, med),  
                    get(doo, (v<<1)+1, max(l, med+1), r, med+1, rr)); 
        }        
        
 //----------------------------------------

        int BinSearch(int[] a, int x, boolean increase){

            int first = 0;
            int last = a.length;
            
            if (increase){
                while (first <= last) {
                    int mid = first + ((last - first) >> 1);                
                    if (x <= a[mid])
                        last = mid;
                    else
                        first = mid + 1;
                }
                return last;
            }else{
                while (first <= last) {
                    int mid = first + ((last - first) >> 1);                
                    if (x > a[mid])
                        last = mid;
                    else
                        first = mid + 1;
                }
                return first;
            }
        }
        
        
//-----------------------------------------
}