LL_FOREACH(problem->rules, rule) {
LL_FOREACH(rule->items, it) {
HASH_FIND_PTR(ordered_variables, it->var, nord);
HASH_FIND_PTR(ordered_variables, &it->var, nord);
if (nord != NULL) {
fprintf(f, "%s%d ", (it->inverse ? "-" : ""), nord->order);
}