Language: C++

#include <iostream>
#include <algorithm>
#include <utility>

using namespace std;

int H, W;
long long res = 1000000000;

int solve() {
    for (int i = 1; i <= H - 1; ++i) {
        long long min_val, max_val;
        min_val = (long long) i * W;
        max_val = (long long) i * W;

        int separated_width;
        if (W % 2) {
            separated_width = W / 2 + 1;
            min_val = min(min_val, (long long) (H - i) * separated_width);
            max_val = max(max_val, (long long) (H - i) * separated_width);

            min_val = min(min_val, (long long) (H - i) * (W - separated_width));
            max_val = max(max_val, (long long) (H - i) * (W - separated_width));

            res = min(res, max_val - min_val);

            min_val = i * W;
            max_val = i * W;
        }
        separated_width = W / 2;
        min_val = min(min_val, (long long) (H - i) * separated_width);
        max_val = max(max_val, (long long) (H - i) * separated_width);

        min_val = min(min_val, (long long) (H - i) * (W - separated_width));
        max_val = max(max_val, (long long) (H - i) * (W - separated_width));

        res = min(res, max_val - min_val);
    }
}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    cin >> H >> W;

    solve();
    swap(&H, &W);
    solve();
    cout << res << endl;
}


Compiler output:
a.cc: In function 'int solve()':
a.cc:39:1: warning: no return statement in function returning non-void [-Wreturn-type]
   39 | }
      | ^
a.cc: In function 'int main()':
a.cc:49:9: error: no matching function for call to 'swap(int*, int*)'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~
In file included from /usr/include/c++/14/bits/exception_ptr.h:41,
                 from /usr/include/c++/14/exception:166,
                 from /usr/include/c++/14/ios:41,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/move.h:226:5: note: candidate: 'std::_Require<std::__not_<std::__is_tuple_like<_Tp> >, std::is_move_constructible<_Tp>, std::is_move_assignable<_Tp> > std::swap(_Tp&, _Tp&) [with _Tp = int*; _Require<__not_<__is_tuple_like<_Tp> >, is_move_constructible<_Tp>, is_move_assignable<_Tp> > = void]' (near match)
  226 |     swap(_Tp& __a, _Tp& __b)
      |     ^~~~
/usr/include/c++/14/bits/move.h:226:5: note:   conversion of argument 2 would be ill-formed:
a.cc:49:14: error: cannot bind non-const lvalue reference of type 'int*&' to an rvalue of type 'int*'
   49 |     swap(&H, &W);
      |              ^~
/usr/include/c++/14/bits/exception_ptr.h:229:5: note: candidate: 'void std::__exception_ptr::swap(exception_ptr&, exception_ptr&)'
  229 |     swap(exception_ptr& __lhs, exception_ptr& __rhs)
      |     ^~~~
/usr/include/c++/14/bits/exception_ptr.h:229:25: note:   no known conversion for argument 1 from 'int*' to 'std::__exception_ptr::exception_ptr&'
  229 |     swap(exception_ptr& __lhs, exception_ptr& __rhs)
      |          ~~~~~~~~~~~~~~~^~~~~
/usr/include/c++/14/bits/move.h:250:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> std::__enable_if_t<((bool)std::__is_swappable<_Tp>::value)> std::swap(_Tp (&)[_Nm], _Tp (&)[_Nm])'
  250 |     swap(_Tp (&__a)[_Nm], _Tp (&__b)[_Nm])
      |     ^~~~
/usr/include/c++/14/bits/move.h:250:5: note:   template argument deduction/substitution failed:
a.cc:49:9: note:   mismatched types '_Tp [_Nm]' and 'int*'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64,
                 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:
/usr/include/c++/14/bits/stl_pair.h:1089:5: note: candidate: 'template<class _T1, class _T2> typename std::enable_if<std::__and_<std::__is_swappable<_T1>, std::__is_swappable<_T2> >::value>::type std::swap(pair<_T1, _T2>&, pair<_T1, _T2>&)'
 1089 |     swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
      |     ^~~~
/usr/include/c++/14/bits/stl_pair.h:1089:5: note:   template argument deduction/substitution failed:
a.cc:49:9: note:   mismatched types 'std::pair<_T1, _T2>' and 'int*'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1106:5: note: candidate: 'template<class _T1, class _T2> typename std::enable_if<(! std::__and_<std::__is_swappable<_T1>, std::__is_swappable<_T2> >::value)>::type std::swap(pair<_T1, _T2>&, pair<_T1, _T2>&)' (deleted)
 1106 |     swap(pair<_T1, _T2>&, pair<_T1, _T2>&) = delete;
      |     ^~~~
/usr/include/c++/14/bits/stl_pair.h:1106:5: note:   template argument deduction/substitution failed:
a.cc:49:9: note:   mismatched types 'std::pair<_T1, _T2>' and 'int*'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~
In file included from /usr/include/c++/14/string:54:
/usr/include/c++/14/bits/basic_string.h:4039:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> void std::swap(__cxx11::basic_string<_CharT, _Traits, _Allocator>&, __cxx11::basic_string<_CharT, _Traits, _Allocator>&)'
 4039 |     swap(basic_string<_CharT, _Traits, _Alloc>& __lhs,
      |     ^~~~
/usr/include/c++/14/bits/basic_string.h:4039:5: note:   template argument deduction/substitution failed:
a.cc:49:9: note:   mismatched types 'std::__cxx11::basic_string<_CharT, _Traits, _Allocator>' and 'int*'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~
In file included from /usr/include/c++/14/bits/memory_resource.h:47,
                 from /usr/include/c++/14/string:68:
/usr/include/c++/14/tuple:2805:5: note: candidate: 'template<class ... _Elements> typename std::enable_if<std::__and_<std::__is_swappable<_Elements>...>::value>::type std::swap(tuple<_UTypes ...>&, tuple<_UTypes ...>&)'
 2805 |     swap(tuple<_Elements...>& __x, tuple<_Elements...>& __y)
      |     ^~~~
/usr/include/c++/14/tuple:2805:5: note:   template argument deduction/substitution failed:
a.cc:49:9: note:   mismatched types 'std::tuple<_UTypes ...>' and 'int*'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~
/usr/include/c++/14/tuple:2823:5: note: candidate: 'template<class ... _Elements> typename std::enable_if<(! std::__and_<std::__is_swappable<_Elements>...>::value)>::type std::swap(tuple<_UTypes ...>&, tuple<_UTypes ...>&)' (deleted)
 2823 |     swap(tuple<_Elements...>&, tuple<_Elements...>&) = delete;
      |     ^~~~
/usr/include/c++/14/tuple:2823:5: note:   template argument deduction/substitution failed:
a.cc:49:9: note:   mismatched types 'std::tuple<_UTypes ...>' and 'int*'
   49 |     swap(&H, &W);
      |     ~~~~^~~~~~~~