Merge sort on [22 10 15 3 8 2]
      merge [10] + [15] -> [10 15]
    merge [22] + [10 15] -> [10 15 22]
      merge [8] + [2] -> [2 8]
    merge [3] + [2 8] -> [2 3 8]
  merge [10 15 22] + [2 3 8] -> [2 3 8 10 15 22]
  result [2 3 8 10 15 22], comparisons = 9, moves = 16
