Study the following series.
9 D V B 5 O @ + A I W P F 1 3 6 G N 8 7
Find what should come in place of the question mark(?)
5O , +I , ? , 1N
There is a gap of 2 between the first characters of each of the given pair. The second character of each pair is increasingly moving one position to the right of the first character.