['5', '2']
[['5', '2']]
['2', '5']
[['5', '2'], ['2', '5']]
['5', '8']
[['5', '2'], ['2', '5'], ['5', '8']]
['7', '8']
[['5', '2'], ['2', '5'], ['5', '8'], ['7', '8']]
['7', '2']
[['5', '2'], ['2', '5'], ['5', '8'], ['7', '8'], ['7', '2']]