Given a list of items in groups, perform certain operations in order to satisfy the constraints required by packaging automation. The conditions are as follows:

1. The first group must contain 1 item only.
2. For all the other groups, the difference between the number of items in adjacent groups must be greater than 1. In other words, for 1 <= i <= n, arr[i] - arr[i - 1] <= 1. To accomplish this, the following operations are available:
   1. Rearrange the groups in any way.
   2. Reduce any group to any number that is >= 1.

Write an algorithm to find the maximum items that can be packaged for the final group of the list given the conditions above.

Example - 1 -- arr = [3, 1, 3, 4]. Output: 4. Explanation: Subtract 1 from the first group making the list [2, 1, 3, 4]. Rearrange the list into [1, 2, 3, 4]. The final maximum of items that can be packaged in the last group is 4.

Example 2 - arr = [1, 1, 1, 1]. Output is 1.