{"raw_statement":[{"iden":"problem statement","content":"There is an $H \\times W$ grid ($H$ vertical, $W$ horizontal), where each square contains a lowercase English letter. Specifically, the letter in the square at the $i$\\-th row and $j$\\-th column is equal to the $j$\\-th character in the string $S_i$.\nSnuke can apply the following operation to this grid any number of times:\n\n*   Choose two different rows and swap them. Or, choose two different columns and swap them.\n\nSnuke wants this grid to be _symmetric_. That is, for any $1 \\leq i \\leq H$ and $1 \\leq j \\leq W$, the letter in the square at the $i$\\-th row and $j$\\-th column and the letter in the square at the $(H + 1 - i)$\\-th row and $(W + 1 - j)$\\-th column should be equal.\nDetermine if Snuke can achieve this objective."},{"iden":"constraints","content":"*   $1 \\leq H \\leq 12$\n*   $1 \\leq W \\leq 12$\n*   $|S_i| = W$\n*   $S_i$ consists of lowercase English letters."},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$H$ $W$\n$S_1$\n$S_2$\n$:$\n$S_H$"},{"iden":"sample input 1","content":"2 3\narc\nrac"},{"iden":"sample output 1","content":"YES\n\nIf the second and third columns from the left are swapped, the grid becomes symmetric, as shown in the image below:\n![image](https://img.atcoder.jp/arc095/2b61caf45e7c5c7311e3944f3418b0bb.png)"},{"iden":"sample input 2","content":"3 7\natcoder\nregular\ncontest"},{"iden":"sample output 2","content":"NO"},{"iden":"sample input 3","content":"12 12\nbimonigaloaf\nfaurwlkbleht\ndexwimqxzxbb\nlxdgyoifcxid\nydxiliocfdgx\nnfoabgilamoi\nibxbdqmzxxwe\npqirylfrcrnf\nwtehfkllbura\nyfrnpflcrirq\nwvcclwgiubrk\nlkbrwgwuiccv"},{"iden":"sample output 3","content":"YES"}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}