body {
  font-family: 'Arial', sans-serif;
  background-color: #f4f4f4;
  color: #333;
  line-height: 1.6;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
}

h1 {
  color: #333;
}

#question {
  background-color: #fff;
  padding: 20px;
  border-radius: 8px;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  margin-bottom: 20px;
  text-align: center;
  font-size: 1.2rem;
}

input[type="number"] {
  padding: 10px;
  border: 1px solid #ddd;
  border-radius: 4px;
  width: 150px;
  font-size: 1rem;
}

button {
  background-color: #007bff;
  color: #fff;
  border: none;
  padding: 10px 20px;
  border-radius: 4px;
  cursor: pointer;
  font-size: 1rem;
  transition: background-color 0.3s ease;
}

button:hover {
  background-color: #0056b3;
}

#result {
  margin-top: 10px;
  font-weight: bold;
}

table {
  width: 80%;
  margin-top: 20px;
  border-collapse: collapse;
  background-color: #fff;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  border-radius: 8px;
}

th, td {
  border: 1px solid #ddd;
  padding: 12px;
  text-align: left;
}

th {
  background-color: #f0f0f0;
}

#stats {
  margin-top: 20px;
  font-size: 1.1rem;
}
/* CSS cũ */

#buttons { /* Thêm một div để chứa 2 nút */
  display: flex;
  justify-content: center; /* Căn giữa các nút */
  gap: 10px; /* Khoảng cách giữa 2 nút */
}