# Instructions

Calculate the Hamming distance between two DNA strands.

We read DNA using the letters C, A, G and T.
Two strands might look like this:

    GAGCCTACTAACGGGAT
    CATCGTAATGACGGCCT
    ^ ^ ^  ^ ^    ^^

They have 7 differences, and therefore the Hamming distance is 7.

## Implementation notes

The Hamming distance is only defined for sequences of equal length, so an attempt to calculate it between sequences of different lengths should not work.
