Language: C++

#include <iostream>
#include <vector>
#include <algorithm>

#define lli long long int
#define REP(i,n) for(lli i=0;i<n;i++)
#define LINF=1LL<<60;

using namespace std;

int main(){

	lli ans = LINF;

	string str;
	cin>>str;

	REP(i,str.size()-1){
		if(str[i]!=str[i+1]){
			ans = min(ans,max(i+1,str.size()-i-1));
		}
	}
	if(ans == LINF)cout<<str.size()<<endl;
	else cout<<ans<<endl;

	return 0;

}

Compiler output:
a.cc:7:9: warning: ISO C++11 requires whitespace after the macro name
    7 | #define LINF=1LL<<60;
      |         ^~~~
a.cc: In function 'int main()':
a.cc:7:13: error: expected primary-expression before '=' token
    7 | #define LINF=1LL<<60;
      |             ^
a.cc:13:19: note: in expansion of macro 'LINF'
   13 |         lli ans = LINF;
      |                   ^~~~
a.cc:20:42: error: no matching function for call to 'max(long long int, long long unsigned int)'
   20 |                         ans = min(ans,max(i+1,str.size()-i-1));
      |                                       ~~~^~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/string:51,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/stl_algobase.h:257:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::max(const _Tp&, const _Tp&)'
  257 |     max(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:257:5: note:   template argument deduction/substitution failed:
a.cc:20:42: note:   deduced conflicting types for parameter 'const _Tp' ('long long int' and 'long long unsigned int')
   20 |                         ans = min(ans,max(i+1,str.size()-i-1));
      |                                       ~~~^~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::max(const _Tp&, const _Tp&, _Compare)'
  303 |     max(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:303:5: note:   candidate expects 3 arguments, 2 provided
In file included from /usr/include/c++/14/algorithm:61,
                 from a.cc:3:
/usr/include/c++/14/bits/stl_algo.h:5706:5: note: candidate: 'template<class _Tp> constexpr _Tp std::max(initializer_list<_Tp>)'
 5706 |     max(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5706:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5716:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::max(initializer_list<_Tp>, _Compare)'
 5716 |     max(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5716:5: note:   template argument deduction/substitution failed:
a.cc:20:42: note:   mismatched types 'std::initializer_list<_Tp>' and 'long long int'
   20 |                         ans = min(ans,max(i+1,str.size()-i-1));
      |                                       ~~~^~~~~~~~~~~~~~~~~~~~
a.cc:7:13: error: expected primary-expression before '=' token
    7 | #define LINF=1LL<<60;
      |             ^
a.cc:23:19: note: in expansion of macro 'LINF'
   23 |         if(ans == LINF)cout<<str.size()<<endl;
      |                   ^~~~
a.cc:23:23: error: expected primary-expression before ')' token
   23 |         if(ans == LINF)cout<<str.size()<<endl;
      |                       ^