def find_it(seq):
    for num in seq:
        if seq.count(num) % 2 == 1:
            return num
    return None

cbcaaea428f03aeea64bad44baec4020bcf8c172
<mask token>

def find_it(seq):
    for num in seq:
        if seq.count(num) % 2 == 1:
            return num
    return None
