Unary notation representation in Turing Machine
A reasonable convention would be to take any enumeration of the integers and use it. For example, this enumeration
$$
0,1,-1,2,-2,3,-3,\ldots
$$
corresponds to this encoding:
$$
\begin{align*}
0 &amp;\to \epsilon \\
1 &amp;\to 1 \\
-1 &amp;\to 11 \\
2 &amp;\to 111 \\
-2 &amp;\to 1111 \\
3 &amp;\to 11111 \\
-3 &amp;\to 111111
\end{align*}
$$