<documents_info>Euler characteristic of a torus,Genus of a surface,Applications of homology theory in image processing</documents_info>
<query>How is the Euler characteristic used to classify surfaces?</query>
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Algorithm
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<documents_info>Euler characteristic of a torus,Genus of a surface,Applications of homology theory in image processing</documents_info>
<query>How is the Euler characteristic used to classify surfaces?</query>
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Catalogue
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<query>How is the Euler characteristic used to classify surfaces?</query>
<documents_info>Euler characteristic of a torus,Genus of a surface,Applications of homology theory in image processing</documents_info>