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

from more_itertools import interleave_longest
T = TypeVar('T')


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


class SortedSet(Generic[T]):
    BUCKET_RATIO = 16
    SPLIT_RATIO = 24

    def __init__(self, a: Iterable[T] = []) -> None:
        "Make a new SortedSet from iterable. / O(N) if sorted and unique / O(N log N)"
        a = list(a)
        n = self.size = len(a)
        if any(a[i] > a[i + 1] for i in range(n - 1)):
            a.sort()
        if any(a[i] >= a[i + 1] for i in range(n - 1)):
            a, b = [], a
            for x in b:
                if not a or a[-1] != x:
                    a.append(x)
        bucket_size = int(math.ceil(math.sqrt(n / self.BUCKET_RATIO)))
        self.a = [a[n * i // bucket_size: n *
                    (i + 1) // bucket_size] for i in range(bucket_size)]

    def __iter__(self) -> Iterator[T]:
        for i in self.a:
            for j in i:
                yield j

    def __reversed__(self) -> Iterator[T]:
        for i in reversed(self.a):
            for j in reversed(i):
                yield j

    def __eq__(self, other) -> bool:
        return list(self) == list(other)

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

    def __repr__(self) -> str:
        return "SortedSet" + str(self.a)

    def __str__(self) -> str:
        s = str(list(self))
        return "{" + s[1: len(s) - 1] + "}"

    def _position(self, x: T) -> Tuple[List[T], int, int]:
        "return the bucket, index of the bucket and position in which x should be. self must not be empty."
        for i, a in enumerate(self.a):
            if x <= a[-1]:
                break
        return (a, i, bisect_left(a, x))

    def __contains__(self, x: T) -> bool:
        if self.size == 0:
            return False
        a, _, i = self._position(x)
        return i != len(a) and a[i] == x

    def add(self, x: T) -> bool:
        "Add an element and return True if added. / O(√N)"
        if self.size == 0:
            self.a = [[x]]
            self.size = 1
            return True
        a, b, i = self._position(x)
        if i != len(a) and a[i] == x:
            return False
        a.insert(i, x)
        self.size += 1
        if len(a) > len(self.a) * self.SPLIT_RATIO:
            mid = len(a) >> 1
            self.a[b:b + 1] = [a[:mid], a[mid:]]
        return True

    def _pop(self, a: List[T], b: int, i: int) -> T:
        ans = a.pop(i)
        self.size -= 1
        if not a:
            del self.a[b]
        return ans

    def discard(self, x: T) -> bool:
        "Remove an element and return True if removed. / O(√N)"
        if self.size == 0:
            return False
        a, b, i = self._position(x)
        if i == len(a) or a[i] != x:
            return False
        self._pop(a, b, i)
        return True

    def lt(self, x: T) -> Optional[T]:
        "Find the largest element < x, or None if it doesn't exist."
        for a in reversed(self.a):
            if a[0] < x:
                return a[bisect_left(a, x) - 1]

    def le(self, x: T) -> Optional[T]:
        "Find the largest element <= x, or None if it doesn't exist."
        for a in reversed(self.a):
            if a[0] <= x:
                return a[bisect_right(a, x) - 1]

    def gt(self, x: T) -> Optional[T]:
        "Find the smallest element > x, or None if it doesn't exist."
        for a in self.a:
            if a[-1] > x:
                return a[bisect_right(a, x)]

    def ge(self, x: T) -> Optional[T]:
        "Find the smallest element >= x, or None if it doesn't exist."
        for a in self.a:
            if a[-1] >= x:
                return a[bisect_left(a, x)]

    def __getitem__(self, i: int) -> T:
        "Return the i-th element."
        if i < 0:
            for a in reversed(self.a):
                i += len(a)
                if i >= 0:
                    return a[i]
        else:
            for a in self.a:
                if i < len(a):
                    return a[i]
                i -= len(a)
        raise IndexError

    def pop(self, i: int = -1) -> T:
        "Pop and return the i-th element."
        if i < 0:
            for b, a in enumerate(reversed(self.a)):
                i += len(a)
                if i >= 0:
                    return self._pop(a, ~b, i)
        else:
            for b, a in enumerate(self.a):
                if i < len(a):
                    return self._pop(a, b, i)
                i -= len(a)
        raise IndexError

    def index(self, x: T) -> int:
        "Count the number of elements < x."
        ans = 0
        for a in self.a:
            if a[-1] >= x:
                return ans + bisect_left(a, x)
            ans += len(a)
        return ans

    def index_right(self, x: T) -> int:
        "Count the number of elements <= x."
        ans = 0
        for a in self.a:
            if a[-1] > x:
                return ans + bisect_right(a, x)
            ans += len(a)
        return ans


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 = SortedSet()
    for idx, (pair_1, pair_2) in enumerate(pairwise(p)):
        pairs_set.add((pair_1, pair_2, idx, idx + 1))
    q = []
    while pairs_set:
        used = pairs_set.pop(0)
        q.extend(used[:2])
        idx_1 = used[2]
        idx_2 = used[3]
        if prev_idxs[idx_1] != -1:
            pairs_set.discard(
                (p[prev_idxs[idx_1]], p[idx_1], prev_idxs[idx_1], idx_1))
        if next_idxs[idx_2] != -1:
            pairs_set.discard(
                (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.add((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()