from heapq import heappush, heappop, heapify

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

pre = dict()
nex = dict()
for i in range(N):
    if i == 0:
        pre[P[i]] = -1
    else:
        pre[P[i]] = P[i-1]
    if i == N-1:
        nex[P[i]] = -1
    else:
        nex[P[i]] = P[i+1]

que = P[:N-1]
heapify(que)
ans = []
S = set()
while que:
    n = heappop(que)
    if n in S:
        continue
    ans.append(n)
    ans.append(nex[n])
    S.add(n)
    S.add(nex[n])
    if nex[nex[n]] == -1:
        if pre[n] != -1:
            S.add(pre[n])
        nex[pre[n]] = -1
    else:
        nex[pre[n]] = nex[nex[n]]
        pre[nex[nex[n]]] = pre[n]
    pre.pop(n)
    pre.pop(nex[n])
    ne = nex[n]
    nex.pop(n)
    nex.pop(ne)

print(*ans)