假设所有自然数排列起来如图所示,55应排在哪个字母下面?248应排在哪个字母下面?
| A | B | C | D |
| 1 | 2 | 3 | 4 |
| 5 | 6 | 7 | 8 |
| 9 | 10 | 11 | 12 |
| . | . | . | . |
| . | . | . | . |
| . | . | . | . |
| A | B | C | D |
| 1 | 2 | 3 | 4 |
| 5 | 6 | 7 | 8 |
| 9 | 10 | 11 | 12 |
| . | . | . | . |
| . | . | . | . |
| . | . | . | . |