import Data.Char
import Data.List
import Control.Monad

main = do
 d <- readLn
 cs <- map (\c -> if c=='o' then True else False) . filter isAlpha <$> getContents
 print (gw2 d cs)

gw2 :: Int -> [Bool] -> Int
gw2 d cs = maximum [chead, clast, maximum (0:cinter)]
 where
  chead = maximum $ map length $ filter head $ group $ replicate d True ++ dropWhile not cs
  clast = maximum $ map length $ filter head $ group $ (reverse . dropWhile not . reverse) cs ++ replicate d True
  cinter = do
   i <- [0 .. 14-d]
   let pat = replicate i False ++ replicate d True ++ replicate (14-(d+i)) False
   let cs' = zipWith (||) pat cs
   guard (length (filter id cs') == length (filter id cs) + d)
   return $ maximum $ (0:) $ map length $ filter head $ group cs'