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 = s a s a + 1 ... s b (1 ≤ a ≤ b ≤ | s |) a substring of string s = s 1 s 2 ... s | s | . A non-empty string s = s 1 s 2 ... s n is called a palindrome if for all i from 1 to n the following fulfills: s i = s n - i + 1 . In other words, palindrome read the same in both directions. String x = x 1 x 2 ... x | x | is lexicographically larger than string y = y 1 y 2 ... y | y | , if either | x | > | y | and x 1 = y 1 , x 2 = y 2 , ... , x | y | = y | y | , or there exists such number r ( r < | x |, r < | y |) , that x 1 = y 1 , x 2 = y 2 , ... , x r = y r and x r + 1 > y r + 1 . Characters in such strings are compared like their ASCII codes. The first line contains integer d ( 1 ≤ d ≤ | s | ). The second line contains a non-empty string s , its length is no more than 4·10 5 characters. The string consists of lowercase English letters. 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).