import Control.Monad
import Data.Maybe
import qualified Data.ByteString.Char8 as BS
import Data.List

readInt = fst . fromJust . BS.readInt
readIntList = map readInt . BS.words
getInt = readInt <$> BS.getLine
getIntList = readIntList <$> BS.getLine

main = do
    [n, k] <- getIntList
    print $ foldl' (plusMod) 0 [(sum [n,n-1..n-i+1] - sum [1..i] + 1)| i <- [k..n+1]]