body {
  padding: 2rem;
  padding-top: 0;
  margin-top: 0;
}
button {
  width: 5rem;
}
input {
  width: 4.5rem;
}
pre {
  max-width: 600px;
}
.flex {
  display: flex;
  gap: 2rem;
}
.flex0 {
  display: flex;
  flex-direction: column;
}
#p_result {
  margin: 0;
  font-size: 1.5rem;
  text-align: center;
}