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