Arrange integers 1- 15 in a triangle such that the upper row consists of 5 integers, all other rows represent each the absolute values of the differences between the adjacent members of the row above so that the 5th row contains one number only.

A bad example:

4 7 15 10 2
3 12 5 8
9 7 *** oops! Can't use 3 again.**

Just wanted to explain the build-up..

Better luck to the solvers!