P1: Repos >= <x1> + <x2>;
P2: Pot >= <x1,x2>;
P3: Att >= <x1,x2>;
P4: Appel >= 2<x1>;
P5: EnCours >= 2<x2>;
P6: EnCours >= <x1>;
P7: #(Jeton) >= 2;
P8: [-,*,-](Message) >= <x2>;