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Language: Annoying painting tool
Description Maybe you wonder what an annoying painting tool is? First of all, the painting tool we speak of supports only black and white. Therefore, a picture consists of a rectangular area of pixels, which are either black or white. Second, there is only one operation how to change the colour of pixels: Select a rectangular area of Initially, all pixels are white. To create a picture, the operation described above can be applied several times. Can you paint a certain picture which you have in mind? Input The input contains several test cases. Each test case starts with one line containing four integers m characters describing the desired pixel values of the i row in the finished painting ('0' indicates white, '1' indicates black).^{th}The last test case is followed by a line containing four zeros. Output For each test case, print the minimum number of operations needed to create the painting, or -1 if it is impossible. Sample Input 3 3 1 1 010 101 010 4 3 2 1 011 110 011 110 3 4 2 2 0110 0111 0000 0 0 0 0 Sample Output 4 6 -1 Source |

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