def find_most_common_element(data):
  """Finds the most common element in a list."""
  counts = {}
  for element in data:
    counts[element] = counts.get(element, 0) + 1

  most_common = None
  max_count = 0
  for element, count in counts.items():
    if count > max_count:
      most_common = element
      max_count = count

  return most_common

import re
text = "Hello, my number is 123-4567."
match = re.search(r'\d{3}', text)
if match:
    print(match.group())
else:
    print("No phone number found.")