Language: C++

/*#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
#include <array>
#include <vector>
#include <deque>
#include <set>
#include <map>
#include <string>
#include <stack>
#include <queue>
#include <unordered_map>
#include <unordered_set>
*/

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

#define int long long
#define pb push_back
#define mp make_pair
#define F first
#define S second
#define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define SORT(c) sort((c).begin(),(c).end())

typedef long long ll;
const ll INF = 1e15+7;
const ll mod = 1e9 + 7;
const int MAX_N = 1e5 + 5;
int dx[] = { -1LL,0,1LL,0 }, dy[] = { 0,1LL,0,-1LL };
vector<ll> prime;

ll inv[MAX_N], fac[MAX_N];

template <class T = ll> T in() { T x; cin >> x; return (x); }
inline ll GCD(ll a, ll b) { ll c; while (b != 0) { c = a % b; a = b; b = c; }return a; }
inline ll LCM(ll a, ll b) { return a * b / GCD(a, b); }
inline ll POW(ll a, ll b) { ll c = 1LL; while (b > 0) { if (b & 1LL) { c = a * c%mod; }a = a * a%mod; b >>= 1LL; }return c; }
inline void _nCr() { fac[0] = 1LL; for (int i = 1LL; i < MAX_N; i++) { fac[i] = fac[i - 1LL] * i%mod; }for (int i = 0; i < MAX_N; i++) { inv[i] = POW(fac[i], mod - 2); } }
inline ll nCr(ll n, ll r) { return (fac[n] * inv[r] % mod)*inv[n - r] % mod; }
inline void PRI(ll n) { bool a[n + 1LL]; for (int i = 0; i < n + 1LL; i++) { a[i] = 1LL; }for (int i = 2; i < n + 1LL; i++) { if (a[i]) { prime.pb(i); ll b = i; while (b <= n) { a[b] = 0; b += i; } } } }

vector<vector<int>> kake(vector<vector<int>> &tim1,vector<vector<int>> &tim2) {
	vector<vector<int>> res = vector<vector<int>>(tim1.size(),vector<int>(tim1[0].size(),0));
	REP (i,tim1.size()) {
		REP (j,tim1[0].size()) {
			REP (k,tim2[0].size()) {
				res[i][k] += tim1[i][j] * tim2[j][k];
				res[i][k] %= mod;
			}
		}
	}
	return res;
}

class UnionFind {
private:
	vector<int> par;
public:
	UnionFind(int N) { par = vector<int>(N, -1LL); }
	int find(int x);
	ll size(int x);
	void unite(int x, int y);
	bool same(int x, int y);
};



//----UnionFind-------------------------------
int UnionFind::find(int x) {
	if (par[x] < 0) return x;
	else return par[x] = find(par[x]);
}

ll UnionFind::size(int x) {
	return -par[find(x)];
}

void UnionFind::unite(int x, int y) {
	x = find(x);
	y = find(y);

	//大きい方に小さい方をくっ付ける
	if (size(x) < size(y)) swap(x, y);
	par[x] += par[y];
	par[y] = x;
}

bool UnionFind::same(int x, int y) {
	x = find(x);
	y = find(y);
	return x == y;
}

//8500±index;

signed main() {
	string s;
	cin >> s;
	int ans = INF;
	FOR (i,1,s) {
		if (s[i] != s[i-1]) {
			ans = min(ans,max(s.size() - i,i));
		}
	}
	cout << ans << endl;
}


Compiler output:
a.cc: In function 'int main()':
a.cc:25:39: error: no match for 'operator<' (operand types are 'long long int' and 'std::string' {aka 'std::__cxx11::basic_string<char>'})
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                    ~~~^~~~
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:17:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::pair<_T1, _T2>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::reverse_iterator<_Iterator>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorR>&)'
 1694 |     operator<(const move_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const move_iterator<_IteratorL>&, const move_iterator<_IteratorL>&)'
 1760 |     operator<(const move_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1760:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'const std::move_iterator<_IteratorL>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
In file included from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/string_view:673:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator<(basic_string_view<_CharT, _Traits>, basic_string_view<_CharT, _Traits>)'
  673 |     operator< (basic_string_view<_CharT, _Traits> __x,
      |     ^~~~~~~~
/usr/include/c++/14/string_view:673:5: note:   template argument deduction/substitution failed:
a.cc:25:42: note:   mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'long long int'
   25 | #define FOR(i,a,b) for(int (i)=(a);(i)<(b);(i)++)
      |                                          ^
a.cc:106:9: note: in expansion of macro 'FOR'
  106 |         FOR (i,1,s) {
      |         ^~~
/usr/include/c++/14/string_view:680:5: note: candidate: 'template<class _CharT, class _Traits> conste