Problem p02983 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define codefor                                                                \
  int test;                                                                    \
  scanf("%d", &test);                                                          \
  while (test--)
#define yn(ans) cout << (ans ? "Yes" : "No") << endl
#define YN(ans) cout << (ans ? "YES" : "NO") << endl
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD = 1000000007;
// 入力系
void scan(int &a) { scanf("%d", &a); }
void scan(long long &a) { scanf("%lld", &a); }
template <class T> void scan(T &a) { cin >> a; }
template <class T> void scan(vector<T> &vec) {
  for (auto &&it : vec)
    scan(it);
}
void in() {}
template <class Head, class... Tail> void in(Head &head, Tail &...tail) {
  scan(head);
  in(tail...);
}
// 出力系
void print(const int &a) { printf("%d", a); }
void print(const long long &a) { printf("%lld", a); }
void print(const double &a) { printf("%.15lf", a); }
template <class T> void print(const T &a) { cout << a; }
template <class T> void print(const vector<T> &vec) {
  if (vec.empty())
    return;
  print(vec[0]);
  for (auto it = vec.begin(); ++it != vec.end();) {
    putchar(' ');
    print(*it);
  }
}
void out() { putchar('\n'); }
template <class T> void out(const T &t) {
  print(t);
  putchar('\n');
}
template <class Head, class... Tail>
void out(const Head &head, const Tail &...tail) {
  print(head);
  putchar(' ');
  out(tail...);
}
// デバッグ系
template <class T> void dprint(const T &a) { cerr << a; }
template <class T> void dprint(const vector<T> &vec) {
  if (vec.empty())
    return;
  cerr << vec[0];
  for (auto it = vec.begin(); ++it != vec.end();) {
    cerr << " " << *it;
  }
}
void debug() { cerr << endl; }
template <class T> void debug(const T &t) {
  dprint(t);
  cerr << endl;
}
template <class Head, class... Tail>
void debug(const Head &head, const Tail &...tail) {
  dprint(head);
  cerr << " ";
  debug(tail...);
}

int main() {
  int l, r, a, ans;
  in(l, r);
  a = l - r + 1;
  if (a >= 2019) {
    out(0);
  } else {
    ans = 2019 * 2019;
    for (int i = l; i < r; i++) {
      for (int j = i + 1; j <= r; j++) {
        ans = min(ans, (i % 2019) * (j % 2019) % 2019);
      }
    }
    out(ans);
  }
}

Fixed submission:
#include <bits/stdc++.h>
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define codefor                                                                \
  int test;                                                                    \
  scanf("%d", &test);                                                          \
  while (test--)
#define yn(ans) cout << (ans ? "Yes" : "No") << endl
#define YN(ans) cout << (ans ? "YES" : "NO") << endl
#define umap unordered_map
#define uset unordered_set
using namespace std;
using ll = long long;
const int MOD = 1000000007;
// 入力系
void scan(int &a) { scanf("%d", &a); }
void scan(long long &a) { scanf("%lld", &a); }
template <class T> void scan(T &a) { cin >> a; }
template <class T> void scan(vector<T> &vec) {
  for (auto &&it : vec)
    scan(it);
}
void in() {}
template <class Head, class... Tail> void in(Head &head, Tail &...tail) {
  scan(head);
  in(tail...);
}
// 出力系
void print(const int &a) { printf("%d", a); }
void print(const long long &a) { printf("%lld", a); }
void print(const double &a) { printf("%.15lf", a); }
template <class T> void print(const T &a) { cout << a; }
template <class T> void print(const vector<T> &vec) {
  if (vec.empty())
    return;
  print(vec[0]);
  for (auto it = vec.begin(); ++it != vec.end();) {
    putchar(' ');
    print(*it);
  }
}
void out() { putchar('\n'); }
template <class T> void out(const T &t) {
  print(t);
  putchar('\n');
}
template <class Head, class... Tail>
void out(const Head &head, const Tail &...tail) {
  print(head);
  putchar(' ');
  out(tail...);
}
// デバッグ系
template <class T> void dprint(const T &a) { cerr << a; }
template <class T> void dprint(const vector<T> &vec) {
  if (vec.empty())
    return;
  cerr << vec[0];
  for (auto it = vec.begin(); ++it != vec.end();) {
    cerr << " " << *it;
  }
}
void debug() { cerr << endl; }
template <class T> void debug(const T &t) {
  dprint(t);
  cerr << endl;
}
template <class Head, class... Tail>
void debug(const Head &head, const Tail &...tail) {
  dprint(head);
  cerr << " ";
  debug(tail...);
}

int main() {
  int l, r, a, ans;
  in(l, r);
  a = r - l + 1;
  if (a >= 2019) {
    out(0);
  } else {
    ans = 2019 * 2019;
    for (int i = l; i < r; i++) {
      for (int j = i + 1; j <= r; j++) {
        ans = min(ans, (i % 2019) * (j % 2019) % 2019);
      }
    }
    out(ans);
  }
}