input: Write a Python function to determine the greatest possible number using the provided digits.
  
  assert find_largest_number([1,2,3],3) == 321
  assert find_largest_number([4,5,6,1],4) == 6541
  assert find_largest_number([1,2,3,9],4) == 9321
output: def find_largest_number(digits, n):
      digits.sort(reverse=True)
      largest_number = int(''.join(map(str, digits[:n])))
      return largest_number