$$
\begin{align}
[\text{main}] &\to [\text {program}] \\
[\text{program}] &\to [\text {Statement*}] \\
[\text{Statement}] &\to
\begin{cases}
Expression \\
If \\
For \\
While \\
When \\
delete \\
using \\
Assign \\
\end{cases} \\
[\text{Operator}] &\to [\text{+ - = /}]\\
[\text{Expression}] &\to [\text{Operand operator Operand}] \\
[\text{Assign}] &\to
\begin{cases}
\text{Type Identifier = Expr} \\
\text{Identifier operator Expr} \\
\end{cases} \\
\end{align}
$$