N = int(input())
P = list(map(int,input().split()))
C = {}
C[P[0]] = [0,P[1]]
for i in range(1,N-1):
    C[P[i]] = [P[i-1],P[i+1]]
C[P[N-1]] = [P[N-2],N+1]
C[0] = [N+1,P[0]]
C[N+1] = [P[N-1],0]
ans = []
for i in range(1,N+1):
    if i not in C:continue
    p = C[i][0]
    n = C[i][1]
    if n==N+1:continue
    ans.append(i)
    ans.append(n)
    nn = C[n][1]
    C[p][1] = nn
    C[nn][0] = p
    del C[i]
    del C[n]
print(*ans)