We want to find a positive integer $a$ such that $\langle a\rangle = \langle 3\rangle \langle 4\rangle$. Since $\langle 3\rangle = \{0, 3\}$ and $\langle 4\rangle = \{0, 4\}$, we have $\langle 3\rangle \langle 4\rangle = \{0, 3, 4, 7\}$. Thus, we want to find a
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