. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 4 4 4 4 4 5 6 . . . 7 4 2.5 2.5 1 - 2 1 - 2 1 - 2 1 - 2 1 - 2 1 - 2 2 - 3 2 - 3 2.5