from itertools import pairwise


def closestNumbers(arr: list[int]) -> list[int]:
    pairs = []
    min_diff = float("inf")
    arr.sort()
    for i, j in pairwise(arr):
        if (diff := abs(i - j)) == min_diff:
            pairs += [i, j]
            continue
        if diff < min_diff:
            min_diff = diff
            pairs = [i, j]
    return pairs