from scipy.sparse import csr_matrix
from scipy.sparse.csgraph import maximum_bipartite_matching

N = int(input())
A = [int(input()) for _ in range(N)]

st = set(A)
if len(st) == 1 and st.pop() < N:
    print(-1)
    exit()

frm, to = [], []
for i, a in enumerate(A):
    for j in range(N):
        if j == a:
            continue
        frm.append(i)
        to.append(j)

matr = csr_matrix(([1] * len(frm), (frm, to)), shape=(N, N))
print(*maximum_bipartite_matching(matr, perm_type='column'), sep='\n')