1-7

  1_2__3___4____5_____6______7_______
  1_2__3___4____5_____6______7_______
        2__3___4____5_____6______7_______
                3___4____5_____6______7_______
                         4____5_____6______7_______
                                    5_____6______7_______
                                                 6______7_______
1_2__3___4____5_____6______7_______
1_2__3___4____5_____6______7_______
2__3___4____5_____6______7_______
3___4____5_____6______7_______
4____5_____6______7_______
5_____6______7_______
6______7_______

^