import qualified Data.List             as L
import qualified Data.Maybe            as M
import qualified Data.ByteString.Char8 as BSC8

main :: IO ()
main = do
  n  <- readLn :: IO Integer
  xs <- readIntegers
  print . flip mod 1000000007 . snd . L.foldl1' (\acc x -> (fst x, (snd acc) + (snd x * nCr (n - 1) (fst x))))  $ zip [0..] xs

readIntegers :: IO [Integer]
readIntegers = map (fst . M.fromJust . BSC8.readInteger) . BSC8.words <$> BSC8.getLine

factorial :: Integer -> Integer
factorial n = product [1..n]

nCr :: Integer -> Integer -> Integer
nCr n r = (product [n-r+1 .. n]) `div` (factorial r)