What word?#5979
Consider a sequence consisting of all possible words of length , where the letters , , and are used at even positions, and the letters and are used at odd positions. This sequence is arranged in lexicographical order. Given the integers and , your task is to find the word that appears in the -th position of this sequence. The words are indexed starting from 1, and the positions within each word are indexed from 0, moving from left to right. If there is no word corresponding to the -th position, output "NO".
The input consists of a single line containing two integers and , separated by a space (0 < N \le 48, 0 \le K \le 5 \cdot 10^{18}).
Output a single line containing the word at the -th position in the sequence, or "NO" if no such word exists.
Example 1