Once upon a time, there was a mountain. Over the mountain there was a temple. In the temple, there was an old monk telling a story. This is the story: Once upon a time, there was a mountain. Over the mountain there was a temple. In the temple, there was an old monk telling a story. This is the story: Once upon a time, there was a mountain. Over the mountain there was a temple. In the temple, there was an old monk telling a story. This is the story......

显然，这是个无穷无尽的故事，yinmz想知道，这个故事的第 $n$ 个字母是什么。

一个数 $n$ ($1\le n\le 10^9$) 。

一个字母 $a$ ,表示这个故事的第n个字母

输出小写字母。