B'After years of hard work scientists invented an absolutely new e-reader display. The new display has a larger resolution, consumes less energy and its production is cheaper. And besides, one can bend it. The only inconvenience is highly unusual management. For that very reason the developers decided to leave the e-readers ' software to programmers. The display is represented by n xe2 x80 x89 xc3 x97 xe2 x80 x89n square of pixels, each of which can be either black or white. The display rows are numbered with integers from 1 to n upside down, the columns are numbered with integers from 1 to n from the left to the right. The display can perform commands like "x, xe2 x80 x89y". When a traditional display fulfills such command, it simply inverts a color of (x, xe2 x80 x89y), where x is the row number and y is the column number. But in our new display every pixel that belongs to at least one of the segments (x, xe2 x80 x89x) xe2 x80 x89- xe2 x80 x89(x, xe2 x80 x89y) and (y, xe2 x80 x89y) xe2 x80 x89- xe2 x80 x89(x, xe2 x80 x89y) (both ends of both segments are included) inverts a color. For example, if initially a display 5 xe2 x80 x89 xc3 x97 xe2 x80 x895 in size is absolutely white, then the sequence of commands (1, xe2 x80 x894), (3, xe2 x80 x895), (5, xe2 x80 x891), (3, xe2 x80 x893) leads to the following changes: You are an e-reader software programmer and you should calculate minimal number of commands needed to display the picture. You can regard all display pixels as initially white. The first line contains number n (1 xe2 x80 x89 xe2 x89 xa4 xe2 x80 x89n xe2 x80 x89 xe2 x89 xa4 xe2 x80 x892000). Next n lines contain n characters each: the description of the picture that needs to be shown. "0" represents the white color and "1" represents the black color. Print one integer z -- the least number of commands needed to display the picture.'...