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 C++14 (GCC 5.4.1) (judge verdict: Runtime Error)

#include <bits/stdc++.h>
using namespace std;

#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define endl "\n"
#define int long long

#define trace1(x)                cerr<<#x<<": "<<x<<endl
#define trace2(x, y)             cerr<<#x<<": "<<x<<" | "<<#y<<": "<<y<<endl
#define trace3(x, y, z)          cerr<<#x<<":" <<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<endl

const int N=2e5+5;

string s;
int n;

bool check(int k)
{
   char cur=s[0];
   int i;
   for(i=1;i<k&&i+k-1<n;i++)
   {
      if(s[i]!=cur)
      {
         if(cur=='0')
            cur='1';
         else
            cur='0';
      }
   }
   bool check=1;
   for(;i<k;i++)
   {
      if(s[i]!=cur)
         check=0;
   }
   cur=s[n-1];
   int ct=0;
   for(i=n-2;i<=k;i--)
   {
      ct++;
      if(s[i]==cur)
      {
         if(cur=='0')
            cur='1';
         else
            cur='0';
      }
      if(ct==k-1)
         break;
   }
   bool check2=1;
   for(;ct<=k;i--)
   {
      if(s[i]!=cur)
         check2=0;
      ct++;
   }
   return (check||check2);
}

int binsearch(int lo, int hi)
{
   while(lo<hi)
   {
      int mid=(lo+hi+1)>>1;
      if(check(mid))
         lo=mid;
      else
         hi=mid-1;
   }
   return lo;
}

int32_t main()
{
   IOS;
   cin>>s;
   n=s.size();
   int ans=binsearch(0 , n);
   cout<<ans;
   return 0;
}