2,130d1 < < < 9 < is_first: 1 < is_last: 0 < < 14 < is_first: 0 < is_last: 1 < < < < 0 < is_first: 1 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 1 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 2 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 3 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 4 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 5 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 6 < is_first: 0 < is_first: 0 -> never < is_last: 1 < is_last: 0 -> never < < < Only one, so should be first and last < < is_first: 1 < is_last: 1 < < < Testing loop < < 0 < is_first: 1 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 5 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 10 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 15 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 20 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 25 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 30 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 35 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 40 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 45 < is_first: 0 < is_first: 0 -> never < is_last: 0 < is_last: 0 -> never < < 50 < is_first: 0 < is_first: 0 -> never < is_last: 1 < is_last: 0 -> never <