from itertools import combinations


def is_kadomatu(a: int, b: int, c: int) -> bool:
    if a == b or b == c or c == a: return False
    if a < b < c: return False
    if a > b > c: return False
    return True


# ゲームに勝つか。先手(turn=1)
def f(turn, used) -> bool:
    res = False
    for a, b, c in combinations(range(N), 3):
        if used[a] or used[b] or used[c]: continue
        if not is_kadomatu(A[a], A[b], A[c]): continue

        used[a] = used[b] = used[c] = turn
        res |= not f(turn+1, used)
        if res and turn == 1:
            return True
        used[a] = used[b] = used[c] = 0

    return res


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

used = [0] * N
iswin = f(1, used)
if not iswin:
    print(-1)
    exit()

ans = [i for i in range(N) if used[i] == 1]
print(*ans)