body {
  font-family: Arial, sans-serif;
  background: #fafafa;
  padding: 40px;
}
h1, h2 {
  margin: 0;
}
.subtitle {
  color: #555;
  margin-bottom: 30px;
}
.problem {
  padding: 12px 0;
  border-bottom: 1px solid #ddd;
}
.rank {
  font-weight: bold;
  margin-right: 10px;
}
.btn {
  margin-left: 20px;
  text-decoration: none;
  border: 1px solid #000;
  padding: 4px 8px;
  font-size: 14px;
}
footer {
  margin-top: 40px;
  font-size: 12px;
  color: #666;
}