{-# LANGUAGE ScopedTypeVariables #-}
import Data.Char
import Data.List.Split
import Data.List
import Data.Maybe
import Data.Set

main = do
    ls <- readFile "6.in"
    putStrLn . show . solveB . parse $ ls where
        parse = (!!0) . words
        solveA = solve 6
        solveB = solve 13
        solve :: Int -> String -> Maybe Int
        solve offset = fmap ((+offset) . fst ) . find (startingSequence . snd) . enumerate . suffixes where
            suffixes = ((fmap Prelude.drop [0..]) <*>) . pure 
            enumerate = zip [1..]
            startingSequence = (==(offset+1)) . size . fromList . Prelude.take (offset+1)