input: Write a function to find all pairs of numbers in a list that sum up to a given number.
  assert find_combos([1, 2, 3, 4], 4) == [[1, 3], [3, 1]]
  assert find_combos([1, 2, 3, 4, 5], 5) == [[1, 4], [2, 3], [3, 2], [4, 1]]
  assert find_combos([1, 2, 3, 4, 5], 6) == [[1, 5], [2, 4], [4, 2], [5, 1]]
output: def find_combos(lst, target):
      result = []
      for i in range(len(lst)):
          for j in range(len(lst)):
              if i != j and lst[i] + lst[j] == target:
                  result.append([lst[i], lst[j]])
      return result