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<math style="font-family: sans-serif">
    <mo>*</mo>
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        <mfrac>
            <msubsup>
                <mi>x</mi>
                <mn>1</mn>
                <mn>2</mn>
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            <munderover>
                <mi>z</mi>
                <mn>3</mn>
                <mn>4</mn>
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        </mfrac>
    </mfenced>
</math>

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