There is such a class of numbers that can be written as the square difference of two natural numbers, such as 3=2**2-1**2, which is called a tree of wisdom, so what is the 1993th wisdom number starting from 1?
有这样一类数，它们可以写作两个自然数的平方差，如3=2**2-1**2，被称作智慧树，那么从1开始，第1993个智慧数是多少？
<gadget id="calculator">1_993 - 1</gadget>
<output>1_992</output>

<gadget id="calculator">1_992 / 3</gadget>
<output>664</output>

<gadget id="calculator">664 * 4</gadget>
<output>2_656</output>

<gadget id="calculator">2_656 + 4</gadget>
<output>2_660</output>

<result>2_660</result>