def main():
    s = input()
    zero = s.count("0")
    one = s.count("1")
    print(min(zero, one) * 2)

main() def main():
    s = input()
    zero = s.count("0")
    one = s.count("1")
    print(min(zero, one) * 2) main s = input() s input() input zero = s.count("0") zero s.count("0") s.count s count "0" one = s.count("1") one s.count("1") s.count s count "1" print(min(zero, one) * 2) print min(zero, one) * 2 min(zero, one) min zero one 2 main() main def main():
    s = input()
    zero = s.count("0")
    one = s.count("1")
    print(min(zero, one) * 2) def main():
    s = input()
    zero = s.count("0")
    one = s.count("1")
    print(min(zero, one) * 2) main
def main():
    s = input()
    zero = s.count("0")
    one = s.count("1")
    print(min(zero, one) * 2)

main()