A/N: I'll let you guys figure out what this is for... ;) *hint* you have the coded version, so use it backwards

A-A
B-C
C-E
D-G
E-I
F-K
G-M
H-O
I-Q
J-S
K-U
L-W
M-Y
N-B
O-D
P-F
Q-H
R-J
S-L
T-N
U-P
V-R
W-T
X-V
Y-X
Z-Z