('A', 'B'), ('C', 'D'), ('E', 'F')
('A', 'C'), ('B', 'E'), ('D', 'F')
('A', 'D'), ('B', 'F'), ('C', 'E')
('A', 'E'), ('B', 'D'), ('C', 'F')
('A', 'F'), ('B', 'C'), ('D', 'E')
Optimal strategy for choosing pairs from a list of combinations