import Data.List

main = do
 n <- readLn
 as <- map read . words <$> getLine
 print (jenga n as)

jenga :: Int -> [Int] -> Int
jenga n as = n - length (ndsc as) + 1
 where ndsc = foldr (\x (a:acc) -> if x == pred a then x:a:acc else a:acc) [n+1]