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.*;

public class StringWithoutPalindromesHashes implements Runnable {
	
	final boolean ONLINE_JUDGE = System.getProperty("ONLINE_JUDGE") != null;
	
	BufferedReader in;
	PrintWriter out;
	StringTokenizer tok;
	
	@Override
	public void run() {
		try {
			long startTime = System.currentTimeMillis();
			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");
			}
			tok = new StringTokenizer("");
			Locale.setDefault(Locale.US);
			solve();
			in.close();
			out.close();
			long endTime = System.currentTimeMillis();
			long totalMemory = Runtime.getRuntime().totalMemory();
			long freeMemory = Runtime.getRuntime().freeMemory();
			System.err.println("Time = " + (endTime - startTime) + " ms");
			System.err.println("Memory = " + ((totalMemory - freeMemory) / 1024) + " KB");
		} catch (Throwable e) {
			e.printStackTrace(System.err);
			System.exit(-1);
		}
	}
	
	String readString() throws IOException {
		while (!tok.hasMoreTokens()) {
			tok = new StringTokenizer(in.readLine());
		}
		return tok.nextToken();
	}
	
	int readInt() throws IOException {
		return Integer.parseInt(readString());
	}
	
	long readLong() throws IOException {
		return Long.parseLong(readString());
	}
	
	double readDouble() throws IOException {
		return Double.parseDouble(readString());
	}
	
	void debug(Object... o) {
		if (!ONLINE_JUDGE) {
			System.err.println(Arrays.deepToString(o));
		}
	}
	
	public static void main(String[] args) {
		new Thread(null, new StringWithoutPalindromesHashes(), "", 256 * 1024 * 1024).start();
	}
	
//------------------------------------------------------------------------------
	
	int d, n;
	char[] s;
	long[] p, h, rh;
	
	void inc(long[] tree, int pos, long delta) {
		for (int i = pos; i < n; i |= (i + 1)) {
			tree[i] += delta;
		}
	}
	
	long getSum(long[] tree, int right) {
		long res = 0;
		for (int i = right; i >= 0; i = (i & (i + 1)) - 1) {
			res += tree[i];
		}
		return res;
	}
	
	long getSum(long[] tree, int left, int right) {
		return getSum(tree, right) - getSum(tree, left - 1);
	}
	
	boolean isPalindrome(int left, int right) {
		long hash = getSum(h, left, right);
		long revHash = getSum(rh, left, right);
		return hash * p[n - right - 1] == revHash * p[left];
	}
	
	void setChar(int pos, char ch) {
		int deltaChar = ch - s[pos];
		s[pos] = ch;
		inc(h, pos, deltaChar * p[pos]);
		inc(rh, pos, deltaChar * p[n - pos - 1]);
	}
	
	void initHashes() {
		p = new long[n];
		h = new long[n];
		rh = new long[n];
		p[0] = 1;
		for (int i = 1; i < n; i++) {
			p[i] = p[i-1] * 161;
		}
		for (int i = 0, j = n-1; i < n; i++, j--) {
			inc(h, i, p[i] * s[i]);
			inc(rh, j, p[i] * s[j]);
		}
	}
	
	void solve() throws IOException {
		d = readInt();
		s = readString().toCharArray();
		n = s.length;
		initHashes();
		int badPos = n-1;
		for (int i = 0; i < n; i++) {
			if (i+d < n && isPalindrome(i, i+d-1)) {
				badPos = i+d-1;
				break;
			}
			if (i+d+1 < n && isPalindrome(i, i+d)) {
				badPos = i+d;
				break;
			}
		}
		while (true) {
			if (badPos < 0) {
				out.println("Impossible");
				return;
			}
			if (s[badPos] == 'z') {
				badPos--;
				continue;
			}
			setChar(badPos, (char)(s[badPos] + 1));
			if (badPos-d+1 >= 0 && isPalindrome(badPos-d+1, badPos)) {
				continue;
			}
			if (badPos-d >= 0 && isPalindrome(badPos-d, badPos)) {
				continue;
			}
			break;
		}
		for (int i = badPos+1; i < n; i++) {
			setChar(i, 'a');
			while (true) {
				if (i-d+1 >= 0 && isPalindrome(i-d+1,i)) {
					setChar(i, (char)(s[i] + 1));
					continue;
				}
				if (i-d >= 0 && isPalindrome(i-d,i)) {
					setChar(i, (char)(s[i] + 1));
					continue;
				}
				break;
			}
		}
		out.println(new String(s));
	}
	
}
