Capacity to Ship Packages

You are given an array `weights` where `weights[i]` is the weight of the i-th package, and an integer `days`. Packages must be shipped in the given order. Each day, you load packages onto a ship with a maximum capacity `C`. You can load any number of packages as long as their total weight does not exceed `C`, and you cannot split a package across days. The ship can make one trip per day. Write a function `ship_within_days(weights, days)` that returns the minimum integer capacity `C` such that all packages can be shipped within `days` days. For example, if `weights = [3, 2, 2, 4, 1, 4]` and `days = 3`, the minimum capacity is `6`. One way to ship: Day 1: [3, 2], Day 2: [2, 4], Day 3: [1, 4]. Constraints: - `1 <= len(weights) <= 50000` - `1 <= weights[i] <= 500` - `1 <= days <= len(weights)` Your implementation must run in O(n log S) time where S is the sum of weights.

```python
>>> ship_within_days([1,2,3,4,5,6,7,8,9,10], 5)
15
>>> ship_within_days([3,2,2,4,1,4], 3)
6
>>> ship_within_days([1,2,3,1,1], 4)
3
```