52. The robot starts coloring natural numbers from 1 in ascending order according to the following rules: Any natural number that can be expressed as the sum of two different composite numbers is colored red, and the rest are colored blue. For example, 23 can be expressed as $15+8$, so 23 is colored red, while 1 cannot be expressed as the sum of two different composite numbers, so it is colored blue. If the numbers colored red are arranged in ascending order, the 2000th one is $\qquad$
answer: 2010