**Guys, help me solve the problem using pure functions. I do not understand the conditions of the problem. And explain in more detail.**

There is a special kind of apple tree that grows apples every day for `n`

days. On the `ith`

day, the tree grows `apples[i]`

apples that will rot after `days[i]`

days, that is on day `i + days[i]`

the apples will be rotten and cannot be eaten. On some days, the apple tree does not grow any apples, which are denoted by `apples[i] == 0`

and `days[i] == 0`

.

You decided to eat **at most** one apple a day (to keep the doctors away). Note that you can keep eating after the first `n`

days.

Given two integer arrays `days`

and `apples`

of length `n`

, return *the maximum number of apples you can eat.*

**Example 1:**

**Input:** apples = [1,2,3,5,2], days = [3,2,1,4,2] **Output:** 7 **Explanation:** You can eat 7 apples: - On the first day, you eat an apple that grew on the first day. - On the second day, you eat an apple that grew on the second day. - On the third day, you eat an apple that grew on the second day. After this day, the apples that grew on the third day rot. - On the fourth to the seventh days, you eat apples that grew on the fourth day.

**Example 2:**

**Input:** apples = [3,0,0,0,0,2], days = [3,0,0,0,0,2] **Output:** 5 **Explanation:** You can eat 5 apples: - On the first to the third day you eat apples that grew on the first day. - Do nothing on the fouth and fifth days. - On the sixth and seventh days you eat apples that grew on the sixth day.