import Data.List

main = do
    [n, m] <- map read . words <$> getLine
    xs <- map (map read . words) . lines <$> getContents
    print . maximum . map (getScore xs) $ permutations [0..n-1]

getScore xs ys = sum . map last $ filter (\i -> (ys !! (i !! 0)) > (ys !! (i !! 1))) xs