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import { ListNode } from "../reverse-linked-list/ListNode.ts";import { get_end_of_list } from "./get_end_of_list.ts";import { get_deep_next_of_list as get_deep_next_of_list } from "../reverse-linked-list-ii/get_deep_next_of_list.ts";export default function mergeInBetween(    list1: ListNode | null,    a: number,    b: number,    list2: ListNode | null,): ListNode | null {    if (!list1) {        return list1;    }    if (!list2) {        return list1;    }    const start_of_first = list1;    const end_of_list2 = get_end_of_list(list2);
    const end_of_first = get_deep_next_of_list(list1, a - 1);    const start_of_third = get_deep_next_of_list(end_of_first, b - a + 2);    end_of_first.next = list2;    end_of_list2.next = start_of_third;    return start_of_first;}