main :: IO ()
main = interact $ show . solve . map read . words

myFloor :: Int -> Int -> Int
myFloor m n = floor $ (fromIntegral m) / (fromIntegral n)

solve :: [Int] -> Int
solve [works, deadline] = yaruki deadline
    where
        yaruki_memo :: [Int]
        yaruki_memo = map yaruki [0..]
        
        yaruki :: Int -> Int
        yaruki 0 = 0
        yaruki x = myFloor (works - (sum $ take x yaruki_memo)) ((deadline - x + 1) ^ 2)