main :: IO ()
main = do
  n <- readLn
  s <- getLine
  print $ solve n s

solve :: Int -> String -> Int
solve n s = if length xs == 0 then n else snd (head xs)
  where
    xs = filter (\(a, b) -> a == "xx") $ zip (zipWith (\a b -> [a, b]) s (tail s)) [1..]