import re
 
def format_phone_number(phone_number):
	pn = re.sub(r'[^\d]', '', phone_number)
	pn = re.sub(r'(\d{3})(?!\d{1}$|$)', r'\1-', pn)
	pn = re.sub(r'(\d{2})(\d{2})', r'\1-\2', pn)
	return pn
 
print(format_phone_number("12"))
print(format_phone_number("123"))
print(format_phone_number("1234"))
print(format_phone_number("12345"))
print(format_phone_number("123456"))
print(format_phone_number("1234567"))
print(format_phone_number("12345678"))
print(format_phone_number("123456789"))
print(format_phone_number("1234567890"))
print(format_phone_number("3-234 234 23 523052 342-234"))
print(format_phone_number("5 34 334 23-4-234 52 345 2-34 52345"))
print(format_phone_number("534 93495 352382 "))

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