In order to provide the logical function you must provide both its minterms and variables.
For example if your function is $F(A,B,C)=A\bar{B}C+\bar{A}BC+AB\bar{C} \quad$ than use 3, 5, 6 as your minterms and A, B, C as variables.
Limit the number of minterms and variables to 16 due to $\LaTeX$ support.
You can also use symbols like $\alpha$ and $\beta$ by simply using their $\LaTeX$ equivalent. For example,
\alpha : $\alpha$
\beta : $\beta$
\gamma :$\gamma$
\phi:$\phi$
\psi:$\psi$
Do not use % , $ and other $\LaTeX$ reserved symbols as variables.