first = input()
x = first[0]
num = [0]
ans = 0
n = 0

for i in range(len(first)):
    if first[i] == x:
        s=1
    else:
        s=-1
    n += 1*s
    num.append(n)
print(num)
n_min = min(num)
n_max = max(num)
for i in range(n_min, n_max):
    le=0
    while num[le] != num[i]:
        le +=1
    ri=len(num)-1
    while num[ri] != num[i]:
        ri -=1
    a = ri - le
    if ans <a:
        ans = a
print(ans)