[Souvarine]

My english is too poor, so I can't explain you the logic for finding solution, but binary tree is in the code tag.
I hope it will help you.

Code:

..........G.......... ..........|.......... ......../...\........ ....../.......\...... .....B.........P..... ..../.\......./.\.... ...Q...A.....D...R... .......|.....|...|... .......C.....E...H... ....../.\............ .....K...F...........