function findDuplicates(numbers: number[]): number[] {
  const seen = new Set<number>()
  const duplicates = new Set<number>()

  numbers.forEach(num => {
    if (seen.has(num)) duplicates.add(num)
    else seen.add(num)
  })
  
  return [...duplicates].sort((a, b) => a - b);
}

// No modificar: necesario para evaluar el resultado.
export { findDuplicates };