In problems on strings one often has to find a string with some particular properties. The problem authors were reluctant to waste time on thinking of a name for some string so they called it good. A string is good if it doesn't have palindrome substrings longer than or equal to d. 

You are given string s, consisting only of lowercase English letters. Find a good string t with length |s|, consisting of lowercase English letters, which is lexicographically larger than s. Of all such strings string t must be lexicographically minimum.

We will call a non-empty string s[a ... b] = sasa + 1... sb (1 ≤ a ≤ b ≤ |s|) a substring of string s = s1s2... s|s|.

A non-empty string s = s1s2... sn is called a palindrome if for all i from 1 to n the following fulfills: si = sn - i + 1. In other words, palindrome read the same in both directions.

String x = x1x2... x|x| is lexicographically larger than string y = y1y2... y|y|, if either |x| > |y| and x1 = y1, x2 = y2, ... , x|y| = y|y|, or there exists such number r (r < |x|, r < |y|), that x1 = y1, x2 = y2, ... , xr = yr and xr + 1 > yr + 1. Characters in such strings are compared like their ASCII codes.

Input

The first line contains integer d (1 ≤ d ≤ |s|).

The second line contains a non-empty string s, its length is no more than 4·105 characters. The string consists of lowercase English letters.

Output

Print the good string that lexicographically follows s, has the same length and consists of only lowercase English letters. If such string does not exist, print "Impossible" (without the quotes).

Examples

Input

3
aaaaaaa


Output

aabbcaa


Input

3
zzyzzzz


Output

Impossible


Input

4
abbabbbabbb


Output

abbbcaaabab
import java.io.* ;
import java.util.*;

import static java.lang.Math.* ;
import static java.util.Arrays.* ;

public class B {
	
	public static void main(String[] args)  {
		
		new B().solveProblem();
		
		out.close();
	}

	static Input in = new Input() ;
	static PrintStream out = new PrintStream(new BufferedOutputStream(System.out));	
	static Output out2 = new Output(out) ;
	
	int k ;
	char[] cs ;
	int n ;
	long[] ma ;
	static final long MOD = 1000000007 ;
	
	public void solveProblem()  {		
	
		k = in.nextInt();
		cs = in.next().toCharArray() ;
		n = cs.length ;
		
		voor = new long[n+1] ;
		na = new long[n+1] ;
		ma = new long[n+1] ;
		ma[0] = 1 ;
		for( int i = 1 ; i <= n ; i++ )
			ma[i] = (ma[i-1]*26) % MOD ;
		
		for( int i = 0 ; i < n ; i++ )
			adjust(voor,i,(ma[i]*(cs[i]-'a'))%MOD) ;
		for( int i = n - 1 ; i >= 0 ; i-- )
			adjust(na,i,(ma[n-1-i]*(cs[i]-'a'))%MOD) ;
		
		int z = k-1 ;

		while( z < n - 1 && !palin(z) )
			z++ ;
		while( true ){
			while( z >= 0 && cs[z] == 'z'){
				cs[z] = 'a' ;
				adjust(voor,z,m(-25*ma[z])) ;
				adjust(na,z,m(-25*ma[n-1-z])) ;
				z-- ;
			}
			if( z < 0 ){
				out.println("Impossible") ;
				return ;
			}
			adjust(voor,z,ma[z]) ;
			adjust(na,z,ma[n-1-z]) ;
			cs[z]++ ;
			
			if( !palin(z))
				break ;
		}
		for( int i = z + 1 ; i < n ; i++){
			for( char c = 'a' ; c <= 'c' ; c++ ){
				adjust(voor,i,m((c-cs[i])*ma[i])) ;
				adjust(na,i,m((c-cs[i])*ma[n-1-i])) ;
				cs[i] = c ;
				if( c == 'c' || !palin(i) )
					break ;
			}
		}
		
		
		out2.wr(cs) ;
		
	}
	
	private boolean palin(int z) {
		return ((z-k>=0) && palin2(z-k,z)) || (z-k+1>=0 &&palin2(z-k+1,z));
	}

	private boolean palin2(int van, int tot) {
		long a = m( rsq(voor,van,tot)*ma[n-1-tot] );
		long b = m( rsq(na,van,tot)*ma[van] ) ;
		return (MOD+ a)%MOD == (MOD + b) % MOD;
	}

	long[] voor ;
	long[] na ;
	
	long rsq( long[] fenwick, int k ){
		long som = 0 ;
		
		while( k > 0 ){
			som = m(som+fenwick[k]) ;
			k -= (k & (-k)) ;
		}
		
		return som ;
		
	}
	
//som is inclusief !
	long rsq( long[] fenwick, int l, int h){
		
		l++ ;
		h++ ;
		
		if( l > h )
			return 0 ;
		if( l == 0 )
			return rsq( fenwick, h ) ;
		return m(rsq( fenwick, h ) - rsq( fenwick, l-1 )) ;
	}
	
	void adjust( long[] fenwick, int k, long v){
		k++ ;
		while( k < fenwick.length ){
			fenwick[k] = (fenwick[k] + v)%MOD ;
			k += (k & (-k)) ;
		}
	}

	
	
	static int[] toArray( ArrayList<Integer> lijst ){
		int[] res = new int[lijst.size()] ;
		int t = 0 ;
		for( int i : lijst)
			res[t++] = i;
		return res ;
	}
	
	static void p( Object ...p){
		System.out.println(Arrays.deepToString(p));
	}
	
	static long m( long g ){
		return (g%MOD) ;
	}
	
	
}

class Input {	
	
	BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
	StringTokenizer tokens ;
	
	public int nextInt(){
		return Integer.parseInt(next()) ;
	}

	public int[] nextInt(int n ){
		int[] res = new int[n] ;
		for( int i = 0 ; i < n ; i++ )
			res[i] = nextInt() ;
		return res ;
	}

	public long nextLong(){
		return Long.parseLong(next()) ;
	}

	public long[] nextLong(int n ){
		long[] res = new long[n] ;
		for( int i = 0 ; i < n ; i++ )
			res[i] = nextLong() ;
		return res ;
	}
	
	public double nextDouble(){
		return Double.parseDouble(next()) ;
	}
	
	public String next(){
		
		try{
			while( tokens == null || !tokens.hasMoreTokens() )
				tokens = new StringTokenizer(buf.readLine()) ;
		}catch( Exception e ){
			e.printStackTrace() ;
		}
		
		return tokens.nextToken() ;
	}

}

class Output {
	
	PrintStream out ;
	
	public Output(PrintStream out) {
		this.out = out;
	}

	void wr( int[] rij ){
		for( int i = 0 ; i < rij.length - 1 ; i++ ) 
			out.print(rij[i] + " ") ;
		out.println(rij[rij.length-1]);		
	}

	void wr( long[] rij ){
		for( int i = 0 ; i < rij.length - 1 ; i++ ) 
			out.print(rij[i] + " ") ;
		out.println(rij[rij.length-1]);		
	}
	
	void wr( char[] rij){
		out.println(new String(rij)) ;
	}
	
}