CF628C Bear and String Distance

Limak is a little polar bear. He likes nice strings — strings of length $ n $ , consisting of lowercase English letters only. The distance between two letters is defined as the difference between their positions in the alphabet. For example, , and . Also, the distance between two nice strings is defined as the sum of distances of corresponding letters. For example, , and . Limak gives you a nice string $ s $ and an integer $ k $ . He challenges you to find any nice string $ s' $ that . Find any $ s' $ satisfying the given conditions, or print "-1" if it's impossible to do so. As input/output can reach huge size it is recommended to use fast input/output methods: for example, prefer to use gets/scanf/printf instead of getline/cin/cout in C++, prefer to use BufferedReader/PrintWriter instead of Scanner/System.out in Java.

The first line contains two integers $ n $ and $ k $ ( $ 1

If there is no string satisfying the given conditions then print "-1" (without the quotes). Otherwise, print any nice string $ s' $ that .