S = input()

length = len(S)
total = 0
for i in list(S):
    total += int(i)

if (length - total) > total:
    answer = total * 2
else:
    answer = (length - total) * 2

print(answer) S = input() S input() input length = len(S) length len(S) len S total = 0 total 0 for i in list(S):
    total += int(i) i list(S) list S total += int(i) total int(i) int i if (length - total) > total:
    answer = total * 2
else:
    answer = (length - total) * 2 (length - total) > total length - total length total total answer = total * 2 answer total * 2 total 2 answer = (length - total) * 2 answer (length - total) * 2 length - total length total 2 print(answer) print answer answer = total * 2 total * 2 answer S = input() input() S length = len(S) len(S) length total = 0 0 total total += int(i) int(i) total answer = (length - total) * 2 (length - total) * 2 answer
S = input()

length = len(S)
total = 0
for i in list(S):
    total += int(i)

if (length - total) > total:
    answer = total * 2
else:
    answer = (length - total) * 2

print(answer)