Its actually very simple! It's just a pattern! For the actual letters, you just skip two letters! This is what I mean:
B and E are two letters apart ( B, C, D, E,) G and J are two letters apart (G, H, I, J,) and so on. and the groups of letters are one apart! ( E, F, G,) (J, K, L,).
So your answer would be: VY
Hope this helps!