function getMedianValue(numbers) {
  const sorted = numbers.slice().sort((a, b) => a - b);
  if (sorted.length % 2 === 1) return sorted[(sorted.length - 1) / 2];
  const lowerValue = sorted[sorted.length / 2 - 1];
  const upperValue = sorted[sorted.length / 2];
  return (lowerValue + upperValue) / 2;
}
@param {Array<number>} numbers
@return {number}