from heapq import heappush, heapify, heappop
from itertools import pairwise
import sys
from bisect import bisect_left, bisect_right
# https://github.com/tatyam-prime/SortedSet/blob/main/SortedSet.py
import math
from collections import defaultdict
from typing import Generic, Iterable, Iterator, List, Tuple, TypeVar, Optional, Hashable


T = TypeVar('T')


def printe(*args, end="\n", **kwargs):
    print(*args, end=end, file=sys.stderr, **kwargs)


T_ = TypeVar('T_', bound=Hashable)


class RemovableHeapQueue:
    def __init__(self, seq: list[T_] = None) -> None:
        self.__queue: list[T_] = []
        if seq is not None:
            self.__queue.extend(seq)
            heapify(self.__queue)
        self.__remove_queue: dict[T_, int] = defaultdict(int)
        self.__length = len(self.__queue)

    def pop(self) -> T_:
        while self.__queue:
            value = heappop(self.__queue)
            if self.__remove_queue[value] > 0:
                self.__remove_queue[value] -= 1
                continue
            self.__length -= 1
            return value
        raise IndexError

    def push(self, item: T_) -> None:
        self.__length += 1
        if self.__remove_queue[item] > 0:
            self.__remove_queue[item] -= 1
            return
        heappush(self.__queue, item)

    @property
    def top(self) -> T_:
        while self.__queue:
            value = self.__queue[0]
            if self.__remove_queue[value] > 0:

                heappop(self.__queue)
                self.__remove_queue[value] -= 1
                continue
            return value
        raise IndexError

    def remove(self, item: T_) -> None:
        self.__remove_queue[item] += 1
        self.__length -= 1

    def __len__(self) -> int:
        return self.__length


def main():
    N = int(input())
    p = list(map(int, input().split()))
    next_idxs = list(range(1, N + 1))
    next_idxs[-1] = -1
    prev_idxs = list(range(-1, N - 1))

    pairs_set = RemovableHeapQueue()
    for idx, (pair_1, pair_2) in enumerate(pairwise(p)):
        pairs_set.push((pair_1, pair_2, idx, idx + 1))

    q = []
    while pairs_set:
        used = pairs_set.pop()
        q.extend(used[:2])
        idx_1 = used[2]
        idx_2 = used[3]
        if prev_idxs[idx_1] != -1:
            pairs_set.remove(
                (p[prev_idxs[idx_1]], p[idx_1], prev_idxs[idx_1], idx_1))
        if next_idxs[idx_2] != -1:
            pairs_set.remove(
                (p[idx_2], p[next_idxs[idx_2]], idx_2, next_idxs[idx_2]))

        if prev_idxs[idx_1] != -1 and next_idxs[idx_2] != -1:
            pairs_set.push((p[prev_idxs[idx_1]],
                           p[next_idxs[idx_2]],
                           prev_idxs[idx_1],
                           next_idxs[idx_2]))

        # 前後関係を更新する
        if prev_idxs[idx_1] != -1:
            if next_idxs[idx_2] != -1:
                next_idxs[prev_idxs[idx_1]] = next_idxs[idx_2]
            else:
                next_idxs[prev_idxs[idx_1]] = -1
        if next_idxs[idx_2] != -1:
            if prev_idxs[idx_1] != -1:
                prev_idxs[next_idxs[idx_2]] = prev_idxs[idx_1]
            else:
                prev_idxs[next_idxs[idx_2]] = -1
    print(*q)


if __name__ == "__main__":
    main()