<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def subword(w):
 """ Function used in the Key Expansion routine that takes a four-byte input word and applies an S-box to each of the four bytes to produce an output word. """

    w = w.reshape(4, 8)
    return SBOX[w[0]] + SBOX[w[1]] + SBOX[w[2]] + SBOX[w[3]]