python3, 80 bytes

Result

WA

Duration

554ms

Code [DL]

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

stdin

MJTXDIHCFWLAFDLHBMSNHUFBKN

stdout

ZUjYLWVMT]bMXUL_TQ^UJeH[T[

stderr

strace