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 Python (3.4.3) (judge verdict: Wrong Answer)



def main(S):
    con = []
    cnt = 1
    now = S[0]

    for c in S[1:]:
        if now != c:
            con.append(cnt)
            cnt = 0
        now = c
        cnt += 1

    con.append(cnt)
    two = [sum(con[i:i + 2]) for i in range(len(con) - 1)]
    three = [sum(con[i:i + 3]) for i in range(len(con) - 2)]
    # print(con)
    # print(two)
    # print(three)

    # for i in range(len(con) - 2):
    #     # print(i, con[i:i+3])
    #     if con[i:i + 3] == [1, 1, 1]:
    #         print('2')
    #         return

    ans = max(con)

    def calc(A, B, add=2):
        ret = -1
        for i in range(len(A)):
            t = A[i]
            f = False
            # print(i, t)
            if 0 <= i - 1 < len(B):
                f = True
                t = min(t, B[i - 1])
            if 0 <= i + add < len(B):
                f = True
                t = min(t, B[i + add])

            # print(i, t)
            if f:
                ret = max(ret, t)

        return ret

    ans = max(ans, calc(three, two))
    ans = max(ans, calc(two, two, add=1))

    print(ans)


S = input()
main(S)