called with [6, 1, 8, 9, 3]
called with [6, 1]
called with [6]
called with [1]
returning [1, 6] 1
called with [8, 9, 3]
called with [8]
called with [9, 3]
called with [9]
called with [3]
returning [3, 9] 1
returning [3, 8, 9] 2
returning [1, 3, 6, 8, 9] 4
4