Problem p02983 (C++)

Buggy submission (status: Time Limit Exceeded):
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <unordered_map>
#include <unordered_set>
#endif
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef vector<ll> vi;
typedef vector<string> vs;
typedef pair<ll, ll> P;
typedef vector<P> vp;
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define REPR(i, n) for (int i = n - 1; i >= 0; i--)
#define FORR(i, n, m) for (int i = n - 1; i >= m; i--)
#define ARR(array) for (int i = 0; i < array.size(); i++)
#define all(in) in.begin(), in.end()
#define ALL(in, K) in, in + K
#define INF 1e18
#define MOD 1000000007
#define SIZE 10005
#define PI 3.14159265358979323846

ll euclidean_gcd(ll a, ll b) {
  if (a < b)
    euclidean_gcd(b, a);
  ll r;
  while ((r = a % b)) {
    a = b;
    b = r;
  }
  return b;
}

double input() {
  ll a;
  cin >> a;
  return a;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll a, b;
  cin >> a >> b;
  ll ans = 2018;
  FOR(i, a, b + 1) FOR(j, a, b + 1) {
    if (i == j)
      continue;
    if (!(i * j)) {
      cout << 0 << endl;
      return 0;
    }
    ans = min((ll)i * (ll)j % 2019, ans);
  }
  cout << ans << endl;
}


Fixed submission:
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <type_traits>
#include <typeindex>
#include <unordered_map>
#include <unordered_set>
#endif
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef vector<ll> vi;
typedef vector<string> vs;
typedef pair<ll, ll> P;
typedef vector<P> vp;
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define REPR(i, n) for (int i = n - 1; i >= 0; i--)
#define FORR(i, n, m) for (int i = n - 1; i >= m; i--)
#define ARR(array) for (int i = 0; i < array.size(); i++)
#define all(in) in.begin(), in.end()
#define ALL(in, K) in, in + K
#define INF 1e18
#define MOD 1000000007
#define SIZE 10005
#define PI 3.14159265358979323846

ll euclidean_gcd(ll a, ll b) {
  if (a < b)
    euclidean_gcd(b, a);
  ll r;
  while ((r = a % b)) {
    a = b;
    b = r;
  }
  return b;
}

double input() {
  ll a;
  cin >> a;
  return a;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ll a, b;
  cin >> a >> b;
  ll ans = 2018;
  FOR(i, a, b + 1) FOR(j, i + 1, b + 1) {
    if (!(j % 2019) || !(i % 2019)) {
      cout << 0 << endl;
      return 0;
    }
    ans = min((ll)i * (ll)j % 2019, ans);
  }
  cout << ans << endl;
}