private static Propagator createProp(IntVar var, Operator op, int cste) {
switch (op) {
case EQ: // X = C
return new PropEqualXC(var, cste);
case NQ: // X =/= C
return new PropNotEqualXC(var, cste);
case GE: // X >= C
return new PropGreaterOrEqualXC(var, cste);
case GT: // X > C --> X >= C + 1
return new PropGreaterOrEqualXC(var, cste + 1);
case LE: // X <= C