B"A binary matrix is called good if every even length square sub-matrix has an odd number of ones. Given a binary matrix a consisting of n rows and m columns, determine the minimum number of cells you need to change to make it good, or report that there is no way to make it good at all. All the terms above have their usual meanings -- refer to the Notes section for their formal definitions. The first line of input contains two integers n and m ( 1 <= q n <= q m <= q 10^6 and n cdot m <= q 10^6 ) -- the number of rows and columns in a , respectively. The following n lines each contain m characters, each of which is one of 0 and 1. If the j -th character on the i -th line is 1, then a_{i,j} = 1 . Similarly, if the j -th character on the i -th line is 0, then a_{i,j} = 0 . Output the minimum number of cells you need to change to make a good, or output -1 if it's not possible at all. In the first case, changing a_{1,1} to 0 and a_{2,2} to 1 is enough. You can verify that there is no way to make the matrix in the second case good. Some definitions -- "...