Shikaku

Description
Shikaku is a region based logic puzzle where the grid is divided up into smaller, rectangular regions.

Rules
The objective is to divide the whole grid into smaller regions, subject to the following rules:
 * 1) Upon completion each tile will be used exactly once, each containing exactly one number.
 * 2) The number in the region will be equal in value to the total of the tiles in that region.
 * 3) All regions must be rectangular.

Example
A standard 10x10 shikaku and its solution.