input: Write a python function to find all unique pairs of numbers in a list that sum up to a specific target value and return the count of such pairs.
  assert find_pairs([1, 2, 3, 4], 7) == 1
  assert find_pairs([1, 5, 3, 7, 9], 10) == 2
  assert find_pairs([2, 4, 6, 8], 12) == 1
  assert find_pairs([1, 1, 1, 1], 2) == 6
output: def find_pairs(numbers, target):
      seen = {}
      pairs = set()
      
      for num in numbers:
          complement = target - num
          if complement in seen:
              pairs.add((min(num, complement), max(num, complement)))
          seen[num] = seen.get(num, 0) + 1
  
      return len(pairs)