Problem:
Score : 500 points

Problem Statement

You are given a string S consisting of 0 and 1.
Find the maximum integer K not greater than |S| such that we can turn all the characters of S into 0 by repeating the following operation some number of times.

Choose a contiguous segment [l,r] in S whose length is at least K (that is, r-l+1\geq K must be satisfied). For each integer i such that l\leq i\leq r, do the following: if S_i is 0, replace it with 1; if S_i is 1, replace it with 0.

Constraints

1\leq |S|\leq 10^5

S_i(1\leq i\leq N) is either 0 or 1.

Input

Input is given from Standard Input in the following format:

S

Output

Print the maximum integer K such that we can turn all the characters of S into 0 by repeating the operation some number of times.

Sample Input 1

010

Sample Output 1

2

We can turn all the characters of S into 0 by the following operations:

Perform the operation on the segment S[1,3] with length 3. S is now 101.

Perform the operation on the segment S[1,2] with length 2. S is now 011.

Perform the operation on the segment S[2,3] with length 2. S is now 000.

Sample Input 2

100000000

Sample Output 2

8

Sample Input 3

00001111

Sample Output 3

4

Solution in Ruby (2.3.3) (judge verdict: Wrong Answer)

s = gets.chars.map(&:to_i)
n1 = s.count(1)
if n1 > s.size - n1
  s.size.times do |i|
    s[i] = s[i] == 1 ? 0 : 1
  end
  n1 = s.size - n1
end

if n1 == 0
  puts s.size
else
  left = 0
  s.each_with_index do |c, i|
    if c == 1
      left = i + 1
      break
    end
  end
  right = 0
  s.size.times do |i|
    if s[-i-1] == 1
      right = i
      break
    end
  end
  STDERR.puts [left, right].join " "
  if n1 == 1
    puts [[left, right].min, [left - 1, right - 1].max].max
  else
    intarvals = []
    cnt = 0
    s.size.times do |i|
      break if left + i + 1 == right
      if s[left + i + 1] == 1
        intarvals << cnt if cnt > 0
        cnt = 0
      else
        cnt += 1
      end
    end
    if intarvals.size > 0
      puts [left, right,intarvals.min].min
    else
      puts [[left, right].min,[left-1, right-1].max].max
    end
  end
end