Gap analisys doesn't work with 3 or more ranges

When there are 3 (or more) ranges, as in the attached tables, gap analysis produces false negatives. This is because what it currently does is inverting a range and check if it can find another range that entirely subsumes the inverted range. The error is in the fact that the inverted range shouldn't be checked against each of the remaining ranges one by one, but against their union.