Toastman came up with a very easy task. He gives it to Appleman, but Appleman doesn't know how to solve it. Can you help him? Given a n × n checkerboard. Each cell of the board has either character 'x', or character 'o'. Is it true that each cell of the board has even number of adjacent cells with 'o'? Two cells of the board are adjacent if they share a side. Input The first line contains an integer n (1 ≤ n ≤ 100). Then n lines follow containing the description of the checkerboard. Each of them contains n characters (either 'x' or 'o') without spaces. Output Print "YES" or "NO" (without the quotes) depending on the answer to the problem. Examples input 3 xxo xox oxx output YES input 4 xxxo xoxo oxox xxxx output NO |
Is it true that each cell of the board has even number of adjacent cells with 'o'? Two cells of the board are adjacent if they share a side. |
input 3 xxo xox oxx |
xxo |
input 3 xxo xox oxx |