Select the letter from among the given options that can replace the question mark (?) in the following series.

Y, S, N, J, ?

G

Y, S, N, J, ?

The logic followed here is :

The difference between consecutive terms is decreasing from 6 and then 5 and 4 and so on , such that:

Y  → (-6) → S → (-5) → N  → (-4) → J → (-3) →G

Thus, the missing term is G