called with [6, 1, 8, 9, 3, 2, 6, 6, 9, 5] 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 called with [2, 6, 6, 9, 5] called with [2, 6] called with [2] called with [6] returning [2, 6] 0 called with [6, 9, 5] called with [6] called with [9, 5] called with [9] called with [5] returning [5, 9] 1 returning [5, 6, 9] 2 returning [2, 5, 6, 6, 9] 3 returning [1, 2, 3, 5, 6, 6, 6, 8, 9, 9] 18 18