Problem p02983 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define lb lower_bound
#define ub upper_bound
#define f first
#define s second

#define sz(x) int((x).size())
#define all(x) (x).begin(), (x).end()

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vd = vector<double>;
using vs = vector<string>;

template <typename T> void ckmin(T &a, const T &b) { a = min(a, b); }
template <typename T> void ckmax(T &a, const T &b) { a = max(a, b); }

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

namespace __input {
template <class T1, class T2> void re(pair<T1, T2> &p);
template <class T> void re(vector<T> &a);
template <class T, size_t SZ> void re(array<T, SZ> &a);

template <class T> void re(T &x) { cin >> x; }
void re(double &x) {
  string t;
  re(t);
  x = stod(t);
}
template <class Arg, class... Args> void re(Arg &first, Args &...rest) {
  re(first);
  re(rest...);
}

template <class T1, class T2> void re(pair<T1, T2> &p) { re(p.f, p.s); }
template <class T> void re(vector<T> &a) { F0R(i, sz(a)) re(a[i]); }
template <class T, size_t SZ> void re(array<T, SZ> &a) { F0R(i, SZ) re(a[i]); }
} // namespace __input
using namespace __input;

namespace __output {
template <class T1, class T2> void pr(const pair<T1, T2> &x);
template <class T, size_t SZ> void pr(const array<T, SZ> &x);
template <class T> void pr(const vector<T> &x);
template <class T> void pr(const set<T> &x);
template <class T1, class T2> void pr(const map<T1, T2> &x);

template <class T> void pr(const T &x) { cout << x; }
template <class Arg, class... Args>
void pr(const Arg &first, const Args &...rest) {
  pr(first);
  pr(rest...);
}

template <class T1, class T2> void pr(const pair<T1, T2> &x) {
  pr("{", x.f, ", ", x.s, "}");
}
template <class T> void prContain(const T &x) {
  pr("{");
  bool fst = 1;
  for (const auto &a : x)
    pr(!fst ? ", " : "", a), fst = 0;
  pr("}");
}
template <class T, size_t SZ> void pr(const array<T, SZ> &x) { prContain(x); }
template <class T> void pr(const vector<T> &x) { prContain(x); }
template <class T> void pr(const set<T> &x) { prContain(x); }
template <class T1, class T2> void pr(const map<T1, T2> &x) { prContain(x); }

void ps() { pr("\n"); }
template <class Arg> void ps(const Arg &first) {
  pr(first);
  ps();
}
template <class Arg, class... Args>
void ps(const Arg &first, const Args &...rest) {
  pr(first, " ");
  ps(rest...);
}
} // namespace __output
using namespace __output;

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);

  int L, R;
  re(L, R);

  vb have(2019);
  FOR(v, L, R + 1)
  have[v % 2019] = true;

  int ans = INT_MAX;
  F0R(a, 2019)
  FOR(b, a + 1, 2019)
  if (have[a] && have[b])
    ckmin(ans, a * b % 2019);
  ps(ans);

  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;

#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define lb lower_bound
#define ub upper_bound
#define f first
#define s second

#define sz(x) int((x).size())
#define all(x) (x).begin(), (x).end()

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vd = vector<double>;
using vs = vector<string>;

template <typename T> void ckmin(T &a, const T &b) { a = min(a, b); }
template <typename T> void ckmax(T &a, const T &b) { a = max(a, b); }

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

namespace __input {
template <class T1, class T2> void re(pair<T1, T2> &p);
template <class T> void re(vector<T> &a);
template <class T, size_t SZ> void re(array<T, SZ> &a);

template <class T> void re(T &x) { cin >> x; }
void re(double &x) {
  string t;
  re(t);
  x = stod(t);
}
template <class Arg, class... Args> void re(Arg &first, Args &...rest) {
  re(first);
  re(rest...);
}

template <class T1, class T2> void re(pair<T1, T2> &p) { re(p.f, p.s); }
template <class T> void re(vector<T> &a) { F0R(i, sz(a)) re(a[i]); }
template <class T, size_t SZ> void re(array<T, SZ> &a) { F0R(i, SZ) re(a[i]); }
} // namespace __input
using namespace __input;

namespace __output {
template <class T1, class T2> void pr(const pair<T1, T2> &x);
template <class T, size_t SZ> void pr(const array<T, SZ> &x);
template <class T> void pr(const vector<T> &x);
template <class T> void pr(const set<T> &x);
template <class T1, class T2> void pr(const map<T1, T2> &x);

template <class T> void pr(const T &x) { cout << x; }
template <class Arg, class... Args>
void pr(const Arg &first, const Args &...rest) {
  pr(first);
  pr(rest...);
}

template <class T1, class T2> void pr(const pair<T1, T2> &x) {
  pr("{", x.f, ", ", x.s, "}");
}
template <class T> void prContain(const T &x) {
  pr("{");
  bool fst = 1;
  for (const auto &a : x)
    pr(!fst ? ", " : "", a), fst = 0;
  pr("}");
}
template <class T, size_t SZ> void pr(const array<T, SZ> &x) { prContain(x); }
template <class T> void pr(const vector<T> &x) { prContain(x); }
template <class T> void pr(const set<T> &x) { prContain(x); }
template <class T1, class T2> void pr(const map<T1, T2> &x) { prContain(x); }

void ps() { pr("\n"); }
template <class Arg> void ps(const Arg &first) {
  pr(first);
  ps();
}
template <class Arg, class... Args>
void ps(const Arg &first, const Args &...rest) {
  pr(first, " ");
  ps(rest...);
}
} // namespace __output
using namespace __output;

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);

  int L, R;
  re(L, R);

  vb have(2019);
  FOR(v, L, min(R + 1, L + 2019))
  have[v % 2019] = true;

  int ans = INT_MAX;
  F0R(a, 2019)
  FOR(b, a + 1, 2019)
  if (have[a] && have[b])
    ckmin(ans, a * b % 2019);
  ps(ans);

  return 0;
}