import qualified Data.Map as Map
import Data.List
import Data.Char

main = do
    input <- getLine
    let filtered = inputFilter input --just throwing out bad input
        Just operation = parser filtered --removes the just
    putStrLn (3 `operation` 7)

inputFilter :: String -> String
inputFilter withjunk = filter (\a -> if '*' == a || '+' == a || '-' == a then True else False) withjunk --throws out everything that's not +-*

parser :: a -> Maybe (Int -> Int -> Int)
parser noJunk = lookup operationMap (head noJunk) --takes the first character in there and tries to get a function out of it

operationMap :: Map.Map (Char, (Int -> Int -> Int)) --map between operation characters and the operation functions themselves
operationMap = Map.fromList
    [('+',Right (+))
    ,('-',Right (-))
    ,('*',Right (*))]