## https://yukicoder.me/problems/no/2740

import heapq

def main():
    N = int(input())
    P = list(map(int, input().split()))

    # 双方向リスト準備
    p_map = {}
    for i in range(N):
        node = {
            "value": P[i],
            "prev" : None,
            "next": None
        }
        p_map[P[i]] = node

        if i > 0:
            p1 = P[i - 1]
            p_node = p_map[p1]
            p_node["next"] = node
            node["prev"] = p_node

    queue = []
    for i in range(N - 1):
        p1 = P[i]
        p2 = P[i + 1]
        heapq.heappush(queue, (p1, p2))
    
    used = [False] * N
    answer = []
    while len(queue) > 0:
        p1, p2  = heapq.heappop(queue)
        if not used[p1 - 1] and not used[p2 - 1]:
            answer.append(p1) 
            answer.append(p2)

            used[p1 - 1] = True 
            used[p2 - 1] = True 
            p_node = p_map[p1]["prev"]
            n_node = p_map[p2]["next"]
            if p_node is not None:
                p_node["next"] = n_node
            if n_node is not None:
                n_node["prev"] = p_node
            
            if p_node is not None and n_node is not None:
                heapq.heappush(queue, (p_node["value"], n_node["value"]))

    
    print(" ".join(map(str, answer)))









    



if __name__ == "__main__":
    main()