# coding: utf-8
import math, copy, collections
from collections import deque
s =input()
n = len(s)
ans = 2
q = deque()
q.append(s[0])

for i in range(1,n):
    if s[i]==q[-1]:
        q.pop()
    else:
        q.append(s[i])
        ans += 1
    #print(q)
print(ans)