**Least Frequently Used**, commonly referred to as **`LFU`**, is a type of *cache algorithm* that manages computer memory. It does so by keeping track of the number of times a block is referenced in the memory and purging the one with the least referencing frequency, once the cache is full and needs more memory.

# Implementation
The easiest method to employ an `LFU` algorithm is by assigning a counter to each block that's loaded into the `cache`, and increment it by one each time it's reaccessed. Once the `cache` is full and more memory needs access, remove the one with the *lowest* `counter` value.

You have to implement two functions, `put(key, value)` and `get(key)`. 

The function **`put(key, value)`** takes `key` and `value` as parameters and assigns the value against the provided key. If the key already exists, it updates the value against that key. 

The function **`get(key)`** takes `key` as a parameter and fetches the value that is stored against that key, subsequently incrementing the counter by one as well.

What is Least Frequently Used (cache replace policy)?

Manages computer memory by purging the least accessed block during cache overflow using reference counters.