function findDuplicates(numbers: number[]): number[] {
  let dup = []
  let count = new Map<number, number>()

  for (let num of numbers){
    count.set(num, (count.get(num) || 0) + 1)
  }
  for (let [num, freq] of count){
    if(freq > 1) {
      dup.push(num)
    }
  }
  
  return dup.sort();
}

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