how to return a missing element in python

1def solution(A):
2    return [value for value in range(min(A),max(A)) if value not in A]
3

1def solution(A):
2    a = set(A)
3    for i, _ in enumerate(A, 1):
4        if i in a:
5            continue
6        return i
7
8solution(A)
9# 3
10