Problem:
Score : 200 points

Problem Statement

AtCoDeer the deer found two rectangles lying on the table, each with height 1 and width W.
If we consider the surface of the desk as a two-dimensional plane, the first rectangle covers the vertical range of [0,1] and the horizontal range of [a,a+W], and the second rectangle covers the vertical range of [1,2] and the horizontal range of [b,b+W], as shown in the following figure:

AtCoDeer will move the second rectangle horizontally so that it connects with the first rectangle.
Find the minimum distance it needs to be moved.

Constraints

All input values are integers.

1≤W≤10^5

1≤a,b≤10^5

Input

The input is given from Standard Input in the following format:

W a b

Output

Print the minimum distance the second rectangle needs to be moved.

Sample Input 1

3 2 6

Sample Output 1

1

This input corresponds to the figure in the statement. In this case, the second rectangle should be moved to the left by a distance of 1.

Sample Input 2

3 1 3

Sample Output 2

0

The rectangles are already connected, and thus no move is needed.

Sample Input 3

5 10 1

Sample Output 3

4

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)

main :: IO ()                                                                                                              
main = map read . words <$> getLine >>= \(w:a:b:_) -> print $ f' w a b                                                     
                                                                                                                           
f w a b                                                                                                                    
  | a <= b && b < a + w = 0                                                                                                
  | b <= a && a < b + w = 0                                                                                                
  | a + w <= b = b - a - w                                                                                                 
  | b + w <= a = a - b - w                                                                                                 
                                                                                                                           
f' w a b                                                                                                                   
  | abs (b - a) < w = 0                                                                                                    
  | otherwise = abs (b - a) - w