(LaTeX) underbrace & overbrace

$\left (a^{m} \right )^{n} = 
\underbrace{
\overbrace{(a \times \cdots \times a)}^{a\text{가 }m\text{개}}
\times 
\overbrace{(a \times \cdots \times a)}^{a\text{가 }m\text{개}} 
\times \cdots \times 
\overbrace{(a \times \cdots \times a)}^{a\text{가 }m\text{개}}}_{\text{괄호가 }n\text{개}
}
=\underbrace{a \times a \times \cdots \times a}_{mn\text{개}}
=a^{mn}$