Construct a standard 1-tape Turing machine M to compute the function sub3, which is defined as follows:
sub3(n) = n-3 if n > 2
0 if n ≤ 2.
Specifically, compute sub3 of a natural number represented in binary. For example, on input 10111, M should output 10100. On input 11101, M should output 11010. (Hint: you may want to define a subroutine.)