main = readLn >>= print . xsum

xsum :: Integer -> Integer
xsum 1 = 1
xsum 2 = 1
xsum n = foldr dsum 0 [1 .. floor (sqrt (fromIntegral d))]
 where
  dsum x acc = if mod d x == 0 then acc + x + div d x else acc
  d = gcd n (div (n*(n-1)) 2)