Language: C++

#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")

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

#define pb push_back
#define F first
#define S second
#define f(i,a,b)  for(int i = a; i < b; i++)
//#define endl '\n'

using ll = long long;
using db = long double;
using row = vector<int>;
using ii = pair<int, int>;

const int N = 5e5 + 5, M = 1e6 + 5, A = 6561, LG = 17, MOD = 1e9 + 7;
const int BLOCK = 1900;
const int BLOCKN = N / BLOCK + 1;
const long double EPS = 1e-7;

  ll N, A, B;
ll simul1(ll A, ll B){
  ll ans = A - 1;
  B -= (A-1);
  A=1;
  ans++;
  B--;
  ans+=(B-A)/2;
  return ans;
}
ll simul2(ll A, ll B){
  return simul1(N-B+1,N-A+1);
}
int main(){
#ifdef ONLINE_JUDGE
  ios_base::sync_with_stdio(0);
  cin.tie(0);
#endif // ONLINE_JUDGE


  cin >> N >> A >> B;

  if((A&1)==(B&1)){
    cout<<(B-A)/2<<'\n';
  } else {
    cout<<min(simul1(A,B),simul2(A,B))<<'\n';
  }

  return 0;
}


Compiler output:
a.cc:23:6: error: conflicting declaration 'll N'
   23 |   ll N, A, B;
      |      ^
a.cc:18:11: note: previous declaration as 'const int N'
   18 | const int N = 5e5 + 5, M = 1e6 + 5, A = 6561, LG = 17, MOD = 1e9 + 7;
      |           ^
a.cc:23:9: error: conflicting declaration 'll A'
   23 |   ll N, A, B;
      |         ^
a.cc:18:37: note: previous declaration as 'const int A'
   18 | const int N = 5e5 + 5, M = 1e6 + 5, A = 6561, LG = 17, MOD = 1e9 + 7;
      |                                     ^
a.cc: In function 'int main()':
a.cc:43:7: error: no match for 'operator>>' (operand types are 'std::istream' {aka 'std::basic_istream<char>'} and 'const int')
   43 |   cin >> N >> A >> B;
      |   ~~~ ^~ ~
      |   |      |
      |   |      const int
      |   std::istream {aka std::basic_istream<char>}
In file included from /usr/include/c++/14/sstream:40,
                 from /usr/include/c++/14/complex:45,
                 from /usr/include/c++/14/ccomplex:39,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:127,
                 from a.cc:4:
/usr/include/c++/14/istream:170:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  170 |       operator>>(bool& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:170:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'bool&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:174:7: note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]' (near match)
  174 |       operator>>(short& __n);
      |       ^~~~~~~~
/usr/include/c++/14/istream:174:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: warning: overflow in conversion from 'int' to 'short int' changes value from '500005' to '-24283' [-Woverflow]
   43 |   cin >> N >> A >> B;
      |          ^
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'short int&' to a value of type 'int'
/usr/include/c++/14/istream:177:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  177 |       operator>>(unsigned short& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:177:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: warning: unsigned conversion from 'int' to 'short unsigned int' changes value from '500005' to '41253' [-Woverflow]
   43 |   cin >> N >> A >> B;
      |          ^
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'short unsigned int&' to a value of type 'int'
/usr/include/c++/14/istream:184:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  184 |       operator>>(unsigned int& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:184:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'unsigned int&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:188:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  188 |       operator>>(long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:188:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'long int&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:192:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  192 |       operator>>(unsigned long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:192:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'long unsigned int&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:199:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  199 |       operator>>(long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:199:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'long long int&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:203:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  203 |       operator>>(unsigned long long& __n)
      |       ^~~~~~~~
/usr/include/c++/14/istream:203:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'long long unsigned int&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:219:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  219 |       operator>>(float& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:219:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'float&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:223:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  223 |       operator>>(double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:223:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'double&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:227:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  227 |       operator>>(long double& __f)
      |       ^~~~~~~~
/usr/include/c++/14/istream:227:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: cannot bind non-const lvalue reference of type 'long double&' to a value of type 'int'
   43 |   cin >> N >> A >> B;
      |          ^
/usr/include/c++/14/istream:328:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  328 |       operator>>(void*& __p)
      |       ^~~~~~~~
/usr/include/c++/14/istream:328:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: invalid conversion from 'int' to 'void*' [-fpermissive]
   43 |   cin >> N >> A >> B;
      |          ^
      |          |
      |          int
a.cc:43:10: error: cannot bind rvalue '(void*)((long int)((int)N))' to 'void*&'
/usr/include/c++/14/istream:122:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__istream_type& (*)(__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>]' (near match)
  122 |       operator>>(__istream_type& (*__pf)(__istream_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:122:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: invalid conversion from 'int' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'} [-fpermissive]
   43 |   cin >> N >> A >> B;
      |          ^
      |          |
      |          int
/usr/include/c++/14/istream:126:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(__ios_type& (*)(__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; __istream_type = std::basic_istream<char>; __ios_type = std::basic_ios<char>]' (near match)
  126 |       operator>>(__ios_type& (*__pf)(__ios_type&))
      |       ^~~~~~~~
/usr/include/c++/14/istream:126:7: note:   conversion of argument 1 would be ill-formed:
a.cc:43:10: error: invalid conversion from 'int' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'} [-fpermissive]
   43 |   cin >> N >> A >> B;
      |          ^
      |          |
      |          int
/usr/include/c++/14/istream:133:7: note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits =