module Main where

import Prelude
import Text.Read
import Data.Maybe
import Data.List
import Debug.Trace
import Data.Monoid

f [] = (First Nothing, Last Nothing)
f (x:xs) = ((,) . First <*> Last $ readMaybe [x]) <> f xs 

g (First x, Last y) = (+) . (*10) <$> x <*> y
--f = sum . take 1 . (zipWith ((+).(*10)) <*> reverse) . catMaybes . map (readMaybe.pure)
main = readFile "input.txt" >>= print . sum . catMaybes . map (g . f) <$> lines