In the case of property which (as a result of its destruction in whole or in part by fire, storm, or other casualty) is compulsorily or involuntarily converted, paragraph (1) shall not apply to such conversion if the taxpayer purchases (during the period specified in section
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(a)(2)(B)) property for use as his principal residence on the site of the converted property. For purposes of subparagraph (A), the adjusted basis of the taxpayer in the residence shall not be adjusted for any gain or loss on a conversion to which this subparagraph applies.