在一个由M*N个小正方形组成的矩形上，依次用两个相等的小正方形大小的矩形（此处所谓相邻是指两个正方形有一条公共边）不重复的覆盖该矩形区域。请构造出该问题的模型，设计算法求解所有可能的覆盖。-In a M* N small squares on the rectangle, followed by two small squares of equal size of the rectangle (here is the so-called two adjacent squares have a common edge) does not duplicate the coverage of the rectangular area. Please construct the problem of the model, the design algorithm for all possible coverage.