import sys
import math
import itertools
import collections
import heapq
import re
import numpy as np
from functools import reduce

rr = lambda: sys.stdin.readline().rstrip()
rs = lambda: sys.stdin.readline().split()
ri = lambda: int(sys.stdin.readline())
rm = lambda: map(int, sys.stdin.readline().split())
rl = lambda: list(map(int, sys.stdin.readline().split()))
inf = float('inf')
mod = 10**9 + 7


s = collections.Counter(rr())
print(min(s['0'], s['1']) * 2)












 import sys sys import math math import itertools itertools import collections collections import heapq heapq import re re import numpy as np numpy from functools import reduce rr = lambda: sys.stdin.readline().rstrip() rr lambda: sys.stdin.readline().rstrip() sys.stdin.readline().rstrip() sys.stdin.readline().rstrip sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline rstrip rs = lambda: sys.stdin.readline().split() rs lambda: sys.stdin.readline().split() sys.stdin.readline().split() sys.stdin.readline().split sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline split ri = lambda: int(sys.stdin.readline()) ri lambda: int(sys.stdin.readline()) int(sys.stdin.readline()) int sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline rm = lambda: map(int, sys.stdin.readline().split()) rm lambda: map(int, sys.stdin.readline().split()) map(int, sys.stdin.readline().split()) map int sys.stdin.readline().split() sys.stdin.readline().split sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline split rl = lambda: list(map(int, sys.stdin.readline().split())) rl lambda: list(map(int, sys.stdin.readline().split())) list(map(int, sys.stdin.readline().split())) list map(int, sys.stdin.readline().split()) map int sys.stdin.readline().split() sys.stdin.readline().split sys.stdin.readline() sys.stdin.readline sys.stdin sys stdin readline split inf = float('inf') inf float('inf') float 'inf' mod = 10**9 + 7 mod 10**9 + 7 10**9 10 9 7 s = collections.Counter(rr()) s collections.Counter(rr()) collections.Counter collections Counter rr() rr print(min(s['0'], s['1']) * 2) print min(s['0'], s['1']) * 2 min(s['0'], s['1']) min s['0'] s '0' s['1'] s '1' 2 rs = lambda: sys.stdin.readline().split() lambda: sys.stdin.readline().split() rs ri = lambda: int(sys.stdin.readline()) lambda: int(sys.stdin.readline()) ri inf = float('inf') float('inf') inf rl = lambda: list(map(int, sys.stdin.readline().split())) lambda: list(map(int, sys.stdin.readline().split())) rl mod = 10**9 + 7 10**9 + 7 mod s = collections.Counter(rr()) collections.Counter(rr()) s rr = lambda: sys.stdin.readline().rstrip() lambda: sys.stdin.readline().rstrip() rr rm = lambda: map(int, sys.stdin.readline().split()) lambda: map(int, sys.stdin.readline().split()) rm
import sys
import math
import itertools
import collections
import heapq
import re
import numpy as np
from functools import reduce

rr = lambda: sys.stdin.readline().rstrip()
rs = lambda: sys.stdin.readline().split()
ri = lambda: int(sys.stdin.readline())
rm = lambda: map(int, sys.stdin.readline().split())
rl = lambda: list(map(int, sys.stdin.readline().split()))
inf = float('inf')
mod = 10**9 + 7


s = collections.Counter(rr())
print(min(s['0'], s['1']) * 2)













