s = input()
z = s.count('0')
print(2 * min(z, len(s) - z))

6f06dd7aa94bfc5adafc1d0d2ec958119919de20
<mask token>

<mask token>
print(2 * min(z, len(s) - z))

s = input()
z = s.count('0')
print(2 * min(z, len(s) - z))
