In the ancient Greek tale, Sisyphus was a king of Ephyra, he was punished for chronic deceitfulness by being compelled to roll an immense stone up a hill every day, only to watch it roll back down, and to repeat this action forever.
Zeus, the God of the universe, shows some mercy for Sisyphus, so he decides to change the way of punishment. He puts N stones with the color of white or black in a line on the hill, everyday when Sisyphus rolls a new stone up the hill, the new stone is added to the back of the old N stones, and the first stone rolls down to the foot of the hill. Then Zeus shows his magic to change the color of the new N stones. Firstly, he looks at a subset S1 of the original N stones, which always includes the first stone, if an odd number of the stones are black, then the newly N-th stone will be black and white otherwise. After the first step is done, he flips the color of another subset S2 of the new N stones, black stone will become white, and white stone will become black vice versa. The following example illustrates how Zeus's magic works.
Consider the case of N = 4, S1 = {1,3}, S2 = {2,4}. Suppose the current stone color state is ●○○○, (○ for white stone, and ● for black stone), the 1st and 3rd stone is black and white respectively, so the new 4th stone will be black, produces ○○○● after the first step. At the second step, the 2nd and 4th stone flip its color, produces ○●○○ in the end.
Zeus tells to Sisyphus that, if one day after the two steps are done, the color of the stones turns to one specific state, he will get his freedom. Now given the current and final stone colors, please compute how many days are needed for Sisyphus's freedom?