select a.F1,min(b.F2) F2
from
(
select F1 from tb t
where not exists(select 1 from tb where abs(F2-t.F1)=1)
) a
join
(
select F2 from tb t
where not exists(select 1 from tb where abs(t.F2-F1)=1)
) b
on a.F1<=b.F2
group by a.F1
/*
F1 F2
----------- -----------
100 129
140 169