# Problem Statement

While building a tower, workers want to lift boxes up from the ground floor to the top floor using elevators. There are two types of boxes. Each box has a weight 50 or 100. Each elevator has enough space for up to two boxes, and can carry a maximum combined weight of 150. Each elevator can only be used once. Given a int[] boxWeights containing the weight of each box, return the minimum number of elevators necessary to transport all the boxes.

# Definition

```Class:              TowerLifts
Method:             leastNumber
Parameters:         int[]
Returns:            int
Method signature:   int leastNumber(int[] boxWeights)
(be sure your method is public)
```

# Constraints

• boxWeights will contain between 1 and 50 elements, inclusive.
• Each element of boxWeights will be equal to 50 or 100.

# Examples

```0)

{50, 100, 50, 50, 50}
Returns: 3
There are two boxes in the first elevator: 50, 100. The second elevator contains: 50 and 50. The third elevator contains only one box: 50.

1)

{100, 100, 50, 100}
Returns: 3

2)

{50, 50}
Returns: 1

3)

{50, 50, 100, 100}
Returns: 2

4)

{50, 50, 100, 100, 50, 100, 50, 50, 50}
Returns: 5
```

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