Vitek loved playing with blocks in kindergarten. Since he was in the senior group, all the blocks had capital English letters. The kindergarten was specialized, preparing children as future linguists and translators, so everyone had to know English. Perhaps they would become language teachers or writers instead — for these professions, knowing English was just as important. Vitek could not remember all the words taught in class, but he could always recall the longest word that read the same forwards and backwards, formed from the letters on the blocks used in the lesson.
The first line contains the number of blocks arranged in front of Vitek, (1 \leq N \leq 100\,000). The second line contains a sequence of letters on the blocks, without spaces.
Output the number of letters in the longest word Vitek remembered.
Example 1