const In : set set prop term iIn = In infix iIn 2000 2000 term nIn = \x:set.\y:set.~ x iIn y term Subq = \x:set.\y:set.!z:set.z iIn x -> z iIn y const SNo : set prop const minus_SNo : set set term - = minus_SNo axiom SNo_minus_SNo: !x:set.SNo x -> SNo - x const SNoS_ : set set const omega : set const nat_p : set prop const SNoLt : set set prop term < = SNoLt infix < 2020 2020 const add_SNo : set set set term + = add_SNo infix + 2281 2280 const ordsucc : set set const Empty : set lemma !x:set.!y:set.SNo x -> nIn x (SNoS_ omega) -> nat_p y -> (- y < x -> x < y -> ?z:set.z iIn SNoS_ omega & (z < x & x < z + ordsucc Empty)) -> - ordsucc y < x -> x < ordsucc y -> SNo y -> SNo - y -> ?z:set.z iIn SNoS_ omega & (z < x & x < z + ordsucc Empty) var x:set var y:set hyp SNo x hyp nIn x (SNoS_ omega) hyp nat_p y hyp - y < x -> x < y -> ?z:set.z iIn SNoS_ omega & (z < x & x < z + ordsucc Empty) hyp - ordsucc y < x hyp x < ordsucc y claim SNo y -> ?z:set.z iIn SNoS_ omega & (z < x & x < z + ordsucc Empty)