Nearly Equal

The *Hamming distance* between two pairs of strings of **equal length** is defined to be the number of positions at which they contain different characters. For example, the Hamming distance between strings $\texttt{"there"}$ and $\texttt{"shire"}$ is $2$ (their first and third characters are different), while the Hamming distance between $\texttt{"order"}$ and $\texttt{"chaos"}$ is $5$, since t