All the stones on the white face - Lycée Vicat (Souillac) Lycée Żmichowska (Varsovie)

Titre du sujet
All the stones on the white face
Établissement
Lycée Vicat (Souillac)
Année
2017-2018
Etablissement(s) jumelé(s)
Lycée Żmichowska (Varsovie)
Résumé
Consider a game board with $n$ columns and $m$ rows. In each square, there is a stone with a white face and a black face. Every time a square is chosen, all the stones around except the one chosen are reversed. With that rule and starting from a situation where all the stones are on the black face, is it possible to reverse all the stones on the white face ?