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f := ((Sqr(x + 2) + Sqr(y - 2) <= 25) and not (Sqr(x) + Sqr(y - 2) <= 16)) or
       ((Sqr(x) + Sqr(y - 2) <= 16) and (Sqr(x - 2) + Sqr(y - 2) <= 9));