[4,9]
[9,4]
—
[]
[1]
[1,2,3]
[3,2,1]
[-3,0,7]
[7,0,-3]
[4,4]
[1,2,3,4]
[4,3,2,1]
[1,2,3,4,5]
[5,4,3,2,1]
[7,7,7,7]
[2,4,6,4,2]
[2,4,6,4]
[4,6,4,2]