X _ _ _ _
  |
X _ _
  |
_ _ _ _ _ _ _ _ _ X  |
_ _ _ _ X  |
_ _ X _ _ _ _
 |
_ _ X _
 |
_ _ _ X _
  |
X _ _ _ _
 |
_ _ X _ _
 |
_ X _ _
 |
X _ _ _
 |
_ _ _ _ X
 |
_ X _ _ _
 |
_ X _ _ _
 |
X _ _ _ _ _
 |
_ _ _ _ X
 |
_ _ _ _ _ X _
 |
_ _ _ X
  |
_ X _ _ _
 |
_ _ _ X _
 |
_ _ _ _ _ _ X
 |
O Pioneers!
O Pioneers!
solution