Compute total revenue from greedy VM rentals

You manage n VM types. VM type i starts with inventory a[i] (number of available instances).

There are m customers arriving one by one. For each customer:

1. The customer rents one instance from the VM type that currently has the largest inventory (if there are ties, any tied type may be chosen).
2. Let maxInv be that largest inventory before the rental.
3. Let minPosInv be the smallest positive inventory among all VM types before the rental (ignore VM types with inventory 0).
4. The revenue from this rental is maxInv + minPosInv .
5. After the rental, the chosen VM type’s inventory decreases by 1.

Assume it is guaranteed that the total initial inventory is at least m.

Task: Compute the total revenue after processing all m customers.

Input

• Integers n , m
• Array a[1..n] of non-negative integers

Output

• A single integer: the total revenue.

Notes

• If multiple VM types share the same maximum inventory, any choice among them leads to a valid simulation.
• minPosInv is always defined because total remaining inventory is positive while customers remain.

Example

If a = [2, 1], m = 2:

• Step 1: maxInv=2 , minPosInv=1 , revenue 3 , inventories -> [1,1]
• Step 2: maxInv=1 , minPosInv=1 , revenue 2 , inventories -> [0,1] Total revenue = 5 .