The natural number sequence 1, 2, 3, 4, 5, 6, ... is eliminated. The principle of elimination is: all natural numbers that cannot be expressed as the sum of two composite numbers are eliminated. For example: "1" should be eliminated; but 12 can be written as the sum of two composite numbers 8 and 4, so it should not be eliminated. If the retained numbers are arranged in ascending order, what is the 2006th number?
对自然数列1，2，3，4，5，6，…进行淘汰，淘汰的原则是：凡不能表示为两个合数之和的自然数均被淘汰．如："1"应被淘汰；但12可以写成两个合数8与4的和，不应被淘汰．被保留下来的数按从小到大的顺序排列，则第2006个数是多少．
<gadget id="calculator">2_006 - 2</gadget>
<output>2_004</output>

<gadget id="calculator">2_004 - 1</gadget>
<output>2_003</output>

<gadget id="calculator">2_003 * 1</gadget>
<output>2_003</output>

<gadget id="calculator">12 + 2_003</gadget>
<output>2_015</output>

<result>2_015</result>