0Good question, Ahn. The quoted sentence is indeed a 01u 00not uncommon02u 00 structure, but it must be used with care, and your effort does not match the criteria required. As you can see, '01i 00not infrequently02i 00' and my own '01i 00not uncommon02i 00' contain a sort of double negative, and their meanings are subtly different (01i 01b 00not in02b 00frequently = rather frequently; 01b 00not un02b 00common = rather common02i 00).
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