The question of how to assign the first

I'm a newbie and I have a question for you:

There is a method of calculating the indicator that the last number is the function m[n+1]=f(m[n] of the previous one, such that the ring is closed.

Since the k-string returned by getRecords is finite, there is always a problem of how to assign the first m[0]

Set to null is not possible, and giving a random value may affect the next value.

Can you please tell me how to handle a first case like this?