python3, 73 bytes

Result

AC

Duration

539ms

Code [DL]

print(''.join([chr((ord(x)+i+1-13)%26+65)for i,x in enumerate(input())]))

stdin

XYZFFJNHZZERLKQQHOTHJWZFAG

stdout

YACJKPUPIJPDYYFGYGMBESWDZG

stderr

strace