input: from typing import List
  
  
  def concatenate_strings(strings: List[str], separator: str) -> str:
      """ Concatenate all elements in the list with a given separator.
      >>> concatenate_strings(["Sample", "Text", "Hello"], "|")
      'Sample|Text|Hello'
      >>> concatenate_strings(["One", "Two", "Three"], "-")
      'One-Two-Three'
      """
output:     result = ""
      for i, s in enumerate(strings):
          result += s
          if i < len(strings) - 1:
              result += separator
      return result