public static int getTotalX(List<int> a, List<int> b) {
  List<int> result = [];
  for (var i = a.Last(); i <= b.Last(); i++) {
    var isFactorOfA = a.Select(s => i % s).All(v => v == 0);
    var isFactorOfB = b.Select(s => s % i).All(v => v == 0);

    if (isFactorOfA && isFactorOfB) result.Add(i);
  }

  return result.Count;
}