H. Head-tail Palindromes - Mashup Trainings Day 3: F0RE1GNERS' Contest - ECNU Online Judge

你可以在这里下载。

单点时限: 2.0 sec

内存限制: 512 MB

样例

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13
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Output

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7
cacbbba

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12
eededdeedede

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NaN

A. Adjacent Seats B. Broken Sequence C. Casino Cheating D. Deprecated Template Book E. Excellent Programmer F. Freshman's Dream G. Generate Problems H. Head-tail Palindromes I. Interesting Nim Game J. Jump K. Kidnapping