Cubes
Vitek loved playing with blocks even in kindergarten. Since he was in the senior group, all the blocks had large English letters. The kindergarten had a special focus, preparing children as future spies—or perhaps diplomats—where knowing English was essential. Although Vitek didn't remember all the words taught in kindergarten very well, he could always recall the longest word that read the same forwards and backwards using the blocks from the lessons. How many blocks were used in the word Vitek remembered?
**Input:** The first line contains the number of blocks laid out in front of Vitek, denoted as N (1 ≤ N ≤ 100000). The next line is a sequence of N letters on the blocks, presented without spaces. **Output:** The number of letters in the longest word Vitek remembered.