Amazon manages a warehouse with sequentially numbered product slots starting from 1. You are given an array inventory[] where inventory[i] is the product ID in ith slot. A perfect slot is a slot where the product ID equals its slot number.

You are allowed to perform the following operation any number of times (possibly zero):

• Choose any index i, remove the product in the ith slot.
• When you remove a product at position i, all products to its right shift one slot to the left.

Determine the maximum number of perfect slots achievable after any number of removals.