C1018 Everyone Write the Princess and Grind the Ink

Qin Feng put the paper on the table and picked up the pen. He started to write 0001 on the paper. He wrote '002' again, and two more words were empty. He wrote '003', which happened to leave a single empty word on the paper.

Qin Feng pointed to the one he had written and said to everyone, "Four numbers, two empty spots, and four more numbers. In this way, the size of the paper is just right