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