How to perform a simple math in cloud ?

I'm using a wifi module, which will send two random numbers (say R1, R2) to the cloud (say Google firebase) and it should perform a basic mathematical operation on another random number produced in cloud (say R3)

operation{
Answer = (R1^R2) mod R3
}

This 'Answer' should be returned to my wifi module. This is a part of an exponential key exchange algorithm. I can handle the code of wifi module to send and receive.
I need help in how I can implement it in cloud database. I'm a newbie to database and stuff. So, pls help me out on how I do this in the cloud.

#-Link-Snipped-# #-Link-Snipped-# #-Link-Snipped-# kindly help me out 😀