---

# # №1
# num = set(input().split())
# print(len(num))
#
# # №21
# str1 = input()
# str2 = input()
# c_c = sorted(list(set(str1) & set(str2)))
# print(c_c)
#
# # №3
# with open('text.txt', 'r', encoding='utf-8') as f:
#     tex = f.read()
# wor = set(tex.lower().split())
# print(len(wor))
#
# # №4
# s1 = set(input().lower().split())
# s2 = set(input().lower().split())
# un_w = s1 ^ s2
# res = sorted([w for w in un_w if len(w) > 3])
# print(res)
#
# # №5
# n = int(input())
# mat = [input().split() for _ in range(n)]
# is_ = True
# for i in range(n):
#     row = mat[i]
#     col = [mat[j][i] for j in range(n)]
#     if len(set(row)) != n or len(set(col)) != n:
#         is_ = False
#         break
# print(is_)
#
# # №6
# numb = [int(x) for x in input().split()]
# seen = set()
# res = []
# for num in numb:
#     if num not in seen:
#         seen.add(num)
#         c = numb.count(num)
#         res.append((num, c))
# print(res)

# №7
with open('ids.txt', 'r') as f:
    min_id, max_id = map(int, f.readline().split())
    reg_id = set(map(int, f.readline().split()))
all_ids = set(range(min_id, max_id + 1))
mis_id = all_ids - reg_id
mis_idl = sorted(list(mis_id), reverse=True)

print(mis_idl)