8. (10 points) On the beach, there is a pile of chestnuts, which belong to four monkeys. They want to divide them equally. The first monkey came, waited and waited but the other monkeys did not come, so it divided the chestnuts into four equal piles, with one left over. It threw the leftover one into the sea and took one of the four piles. The second monkey came, and without waiting for the others, it divided the remaining chestnuts into four equal piles, with one left over. It threw away the leftover one and took one pile. The third monkey did the same, dividing the remaining chestnuts into four equal piles, throwing away the leftover one, and taking one pile. The last monkey also divided the remaining chestnuts into four equal piles, threw away the leftover one, and took one pile. So, the original pile of chestnuts had at least $\qquad$ chestnuts.
【Analysis】To solve the problem, we need to draw a reverse diagram and observe that each time the number is 1 more than a multiple of 4. Therefore, we should consider adding 3 to make it a multiple of 4. We notice that the number for the fourth monkey is a multiple of 4, for the third monkey it is a multiple of 16, and so on, which allows us to solve the problem.

【Solution】To find the minimum number, we start from the smallest possible number, where each time a monkey comes, the number is 1 more than a multiple of 4. We will work backwards from the fourth monkey.

Each time a monkey takes $\frac{1}{4}$, leaving $\frac{3}{4}$. The remainder is always 1. So, when the fourth monkey comes, we consider giving it 3 more to make it a multiple of 4.

The total number for the third monkey is also 3 more than the original, making it a multiple of 4. Therefore, the number when the third monkey comes should be $4 \times 4 = 16$.

The total number for the second monkey is also 3 more than the original, making it a multiple of 4. Therefore, the number when the second monkey comes should be $4 \times 4 \times 4 = 64$.

The total number for the first monkey is also 3 more than the original, making it a multiple of 4. Therefore, the number when the first monkey comes should be $4 \times 4 \times 4 \times 4 = 256$.

Since the original number should be at least $256 - 3 = 253$.
Therefore, the answer is: 253