Stuck with index power

In my local editor this code works, but here I`ve got mistake like "TypeError: 'int' object is not subscriptable, index_power, 6"

Why ?

def index_power(array, n):
"""
    Find Nth power of the element with index N.
"""
N=(array[0][array[-1]])**array[-1]
return N

if name == 'main': #These "asserts" using only for self-checking and not necessary for auto-testing assert indexpower([1, 2, 3, 4], 2) == 9, "Square" assert indexpower([1, 3, 10, 100], 3) == 1000000, "Cube" assert indexpower([0, 1], 0) == 1, "Zero power" assert indexpower([1, 2], 3) == -1, "IndexError"