# Define a function that takes in two non-negative integers a and b and returns the last decimal digit of a^b.
# Note that a and b may be very large!
# For example, the last decimal digit of 9^7 is 9, since 9^7 = 4782969.
# The last decimal digit of (2^200)^(2^300), which has over 10^92 decimal digits, is 6.
# Also, please take 0^0 to be 1.
# You may assume that the input will always be valid.

# Examples
# last_digit(4, 1)                # returns 4
# last_digit(4, 2)                # returns 6
# last_digit(9, 7)                # returns 9
# last_digit(10, 10 ** 10)        # returns 0
# last_digit(2 ** 200, 2 ** 300)  # returns 6

def last_digit(n1, n2):
    return
