(<=> (>= ?X ?Y) (Or (> ?X ?Y) (= ?X ?Y)))
(>= ?X 0) (=> (Nonnegative-Integer ?X) (>= ?X 0)) (<- (Abs ?X) (If (>= ?X 0) ?X (- ?X))) (<=> (>= ?X ?Y) (Or (> ?X ?Y) (= ?X ?Y)))