def make_1ton_missing_number(n, to_remove):
    return [a for a in range(1, n + 1) if a != to_remove]

n = 12
l = make_1ton_missing_number(n, 8)

l

[1, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12]
def get_missing_number(l1ton, n):
    res = 0
    
    for val in range(1, n + 1):
        res ^= val
        
    for val in l1ton:
        res ^= val
    
    return res

get_missing_number(l, n)

8
8 ^ 8

0
0 ^ 8

8