Give an equilateral polygon with 20 vertices, A1, A2, … , A20. At the vertices A1, A2, write the sign (−). At the rest of vertices, write the sign (+). The game is implemented as follow: each time the sign is changed simultaneously at 5 consecutive vertices of the polygon, the sign (−) becomes a sign (+), the sign (+) becomes a sign (−). After some changes, does the game have the results as: at the vertices A3, A4, write a sign (−), at the rest of the vertices, write sign (+)? Why?