{"problem":{"name":"Symmetric Grid","description":{"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 equ","description_type":"Markdown"},"platform":"AtCoder","limit":{"time_limit":2000,"memory_limit":262144},"difficulty":"None","is_remote":true,"is_sync":true,"sync_url":null,"sign":"arc095_c"},"statements":[{"statement_type":"Markdown","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.\n\n## Constraints\n\n*   $1 \\leq H \\leq 12$\n*   $1 \\leq W \\leq 12$\n*   $|S_i| = W$\n*   $S_i$ consists of lowercase English letters.\n\n## Input\n\nInput is given from Standard Input in the following format:\n\n$H$ $W$\n$S_1$\n$S_2$\n$:$\n$S_H$\n\n[samples]","is_translate":false,"language":"English"}],"meta":{"iden":"arc095_c","tags":[],"sample_group":[["2 3\narc\nrac","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)"],["3 7\natcoder\nregular\ncontest","NO"],["12 12\nbimonigaloaf\nfaurwlkbleht\ndexwimqxzxbb\nlxdgyoifcxid\nydxiliocfdgx\nnfoabgilamoi\nibxbdqmzxxwe\npqirylfrcrnf\nwtehfkllbura\nyfrnpflcrirq\nwvcclwgiubrk\nlkbrwgwuiccv","YES"]],"created_at":"2026-03-03 11:01:14"}}