Problem p02727 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rrep(i, n) for (int i = n - 1; i >= 0; --i)
#define fi first
#define se second
using namespace std;
using lint = long long;
using uint = unsigned int;
using ulint = unsigned long long;
using ldouble = long double;
using pii = pair<int, int>;
using pli = pair<lint, lint>;
using pdd = pair<double, double>;
using pld = pair<ldouble, ldouble>;
using v1i = vector<int>;
using v1li = vector<lint>;
using v2i = vector<vector<int>>;
using v2li = vector<vector<lint>>;
using v3i = vector<vector<vector<int>>>;
using v3li = vector<vector<vector<lint>>>;
using v1b = vector<bool>;
using v2b = vector<vector<bool>>;
using v3b = vector<vector<vector<bool>>>;
using v1c = vector<char>;
using v2c = vector<vector<char>>;
using v3c = vector<vector<vector<char>>>;
constexpr lint mod1 = 1e9 + 7;
constexpr lint mod2 = 998244353;

int main() {
  lint s = 0, x, y, a, b, c, k = 0;
  cin >> x >> y >> a >> b >> c;
  v1i t(a), u(b), v(c);
  rep(i, a) cin >> t[i];
  rep(i, b) cin >> u[i];
  rep(i, c) cin >> v[i];
  sort(t.begin(), t.end());
  reverse(t.begin(), t.end());
  sort(u.begin(), u.end());
  reverse(u.begin(), u.end());
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  while (x > 0 || y > 0) {
    if (v[k] - t[x - 1] > v[k] - u[y - 1] && x > 0) {
      if (v[k] > t[x - 1] && k < c) {
        s += v[k];
        ++k;
      } else
        s += t[x - 1];
      --x;
    } else {
      if (v[k] > u[y - 1] && k < c) {
        s += v[k];
        ++k;
      } else
        s += u[y - 1];
      --y;
    }
  }
  cout << s << endl;
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
#define rrep(i, n) for (int i = n - 1; i >= 0; --i)
#define fi first
#define se second
using namespace std;
using lint = long long;
using uint = unsigned int;
using ulint = unsigned long long;
using ldouble = long double;
using pii = pair<int, int>;
using pli = pair<lint, lint>;
using pdd = pair<double, double>;
using pld = pair<ldouble, ldouble>;
using v1i = vector<int>;
using v1li = vector<lint>;
using v2i = vector<vector<int>>;
using v2li = vector<vector<lint>>;
using v3i = vector<vector<vector<int>>>;
using v3li = vector<vector<vector<lint>>>;
using v1b = vector<bool>;
using v2b = vector<vector<bool>>;
using v3b = vector<vector<vector<bool>>>;
using v1c = vector<char>;
using v2c = vector<vector<char>>;
using v3c = vector<vector<vector<char>>>;
constexpr lint mod1 = 1e9 + 7;
constexpr lint mod2 = 998244353;

int main() {
  lint s = 0, x, y, a, b, c, k = 0;
  cin >> x >> y >> a >> b >> c;
  v1i t(a), u(b), v(c);
  rep(i, a) cin >> t[i];
  rep(i, b) cin >> u[i];
  rep(i, c) cin >> v[i];
  sort(t.begin(), t.end());
  reverse(t.begin(), t.end());
  sort(u.begin(), u.end());
  reverse(u.begin(), u.end());
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  while (x > 0 || y > 0) {
    if ((v[k] - t[x - 1] > v[k] - u[y - 1] && x > 0) || y == 0) {
      if (v[k] > t[x - 1] && k < c) {
        s += v[k];
        ++k;
      } else
        s += t[x - 1];
      --x;
    } else {
      if (v[k] > u[y - 1] && k < c) {
        s += v[k];
        ++k;
      } else
        s += u[y - 1];
      --y;
    }
  }
  cout << s << endl;
  return 0;
}