Language: C++

#include<bits/stdc++.h>
using namespace std;
// make pair, tuple
// __gcd(int, int);
// bool isPrime(int n){
//       if(n <= 1)return false;
//       if(n <= 3)return true;
//       if(n % 2 == 0 || n % 3 == 0)return false;
//       for(int i = 5;i * i <= n;i += 6){
//             if(n % i == 0 || n % (i + 2) == 0)return false;
//       }
//       return true;
// }
// int countSubString(string s, string temp){
//       int ans = 0;
//       size_t f = s.find(temp);
//       while(f != string::npos){
//             ans++;
//             f = s.find(temp, f + 1);
//       }
//       return ans;
// }
// 
// #Count leading & trailing zero of an integer bits
// __builtin_clz(n);
// __builtin_clzll(n);
//
// #Count 1s bits of an integer
// __builtin_popcount(n);
// __builtin_popcountll(n);
//
// #Error checking
// assert(n == 3);
// 
// #Error Printing
// cerr << "Some thing";

int main(){
    long long int l,r;cin >> l >> r;
    r = min(r, l + 2 * 2019);
    int ans = INT_MAX;
    for(long long int i = l;i < r;i++){
        for(long long int j = i + 1;j <= r;j++){
            ans = min(ans, (i * j) % 2019);
        }
    }
    cout << ans;
}

Compiler output:
a.cc: In function 'int main()':
a.cc:44:22: error: no matching function for call to 'min(int&, long long int)'
   44 |             ans = min(ans, (i * j) % 2019);
      |                   ~~~^~~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 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:   template argument deduction/substitution failed:
a.cc:44:22: note:   deduced conflicting types for parameter 'const _Tp' ('int' and 'long long int')
   44 |             ans = min(ans, (i * j) % 2019);
      |                   ~~~^~~~~~~~~~~~~~~~~~~~~
/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, 2 provided
In file included from /usr/include/c++/14/algorithm:61:
/usr/include/c++/14/bits/stl_algo.h:5686:5: note: candidate: 'template<class _Tp> constexpr _Tp std::min(initializer_list<_Tp>)'
 5686 |     min(initializer_list<_Tp> __l)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5686:5: note:   candidate expects 1 argument, 2 provided
/usr/include/c++/14/bits/stl_algo.h:5696:5: note: candidate: 'template<class _Tp, class _Compare> constexpr _Tp std::min(initializer_list<_Tp>, _Compare)'
 5696 |     min(initializer_list<_Tp> __l, _Compare __comp)
      |     ^~~
/usr/include/c++/14/bits/stl_algo.h:5696:5: note:   template argument deduction/substitution failed:
a.cc:44:22: note:   mismatched types 'std::initializer_list<_Tp>' and 'int'
   44 |             ans = min(ans, (i * j) % 2019);
      |                   ~~~^~~~~~~~~~~~~~~~~~~~~