Language: C++

#include <iostream>
using namespace std;

int main()
{
    uint64_t L, R;
    cin >> L >> R;
    uint64_t m = (L % 2019 * (L + 1) % 2019) % 2019;
    for (uint64_t i = L; i < R; ++i) {
        for (uint64_t j = i + 1; j <= R; ++j) {
            if (j - i >= 2019) {
                m = 0;
                break;
            }
            m = min({(i % 2019 * j % 2019) % 2019});
        }
    }

    cout << m << endl;

    return 0;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:6:5: error: 'uint64_t' was not declared in this scope
    6 |     uint64_t L, R;
      |     ^~~~~~~~
a.cc:2:1: note: 'uint64_t' is defined in header '<cstdint>'; this is probably fixable by adding '#include <cstdint>'
    1 | #include <iostream>
  +++ |+#include <cstdint>
    2 | using namespace std;
a.cc:7:12: error: 'L' was not declared in this scope
    7 |     cin >> L >> R;
      |            ^
a.cc:7:17: error: 'R' was not declared in this scope
    7 |     cin >> L >> R;
      |                 ^
a.cc:8:13: error: expected ';' before 'm'
    8 |     uint64_t m = (L % 2019 * (L + 1) % 2019) % 2019;
      |             ^~
      |             ;
a.cc:9:18: error: expected ';' before 'i'
    9 |     for (uint64_t i = L; i < R; ++i) {
      |                  ^~
      |                  ;
a.cc:9:26: error: 'i' was not declared in this scope
    9 |     for (uint64_t i = L; i < R; ++i) {
      |                          ^
a.cc:10:22: error: expected ';' before 'j'
   10 |         for (uint64_t j = i + 1; j <= R; ++j) {
      |                      ^~
      |                      ;
a.cc:10:34: error: 'j' was not declared in this scope
   10 |         for (uint64_t j = i + 1; j <= R; ++j) {
      |                                  ^
a.cc:12:17: error: 'm' was not declared in this scope; did you mean 'tm'?
   12 |                 m = 0;
      |                 ^
      |                 tm
a.cc:15:13: error: 'm' was not declared in this scope; did you mean 'tm'?
   15 |             m = min({(i % 2019 * j % 2019) % 2019});
      |             ^
      |             tm
a.cc:15:20: error: no matching function for call to 'min(<brace-enclosed initializer list>)'
   15 |             m = min({(i % 2019 * j % 2019) % 2019});
      |                 ~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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:233:5: note: candidate: 'template<class _Tp> constexpr const _Tp& std::min(const _Tp&, const _Tp&)'
  233 |     min(const _Tp& __a, const _Tp& __b)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:233:5: note:   candidate expects 2 arguments, 1 provided
/usr/include/c++/14/bits/stl_algobase.h:281:5: note: candidate: 'template<class _Tp, class _Compare> constexpr const _Tp& std::min(const _Tp&, const _Tp&, _Compare)'
  281 |     min(const _Tp& __a, const _Tp& __b, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algobase.h:281:5: note:   candidate expects 3 arguments, 1 provided
a.cc:19:13: error: 'm' was not declared in this scope; did you mean 'tm'?
   19 |     cout << m << endl;
      |             ^
      |             tm