-- Try yukicoder
-- author: Leonardone @ NEETSDKASU


main = interact $ show . solve . map read . words
 
solve [a, b] = f True 1 a b

f ex cnt 0 0 = if ex then max 1 (div cnt 2) else 0
f ex cnt a b = f e c ad bd
    where
        (ad, am) = divMod a 2
        (bd, bm) = divMod b 2
        e = ex && not (am == 1 && bm == 0)
        c = cnt * if am == 0 && bm == 1 then 2 else 1