private static List<AccountAction> merge(List<? extends AccountAction>... lists) {
        int size = 0;
        for (List<? extends AccountAction> actions : lists) {
            size += actions.size();
        }
        List<AccountAction> actions = new ArrayList<>(size);
        int[] counters = new int[lists.length];
        while (actions.size() < size) {
            int n = -1;
            int version = Integer.MAX_VALUE;
            for (int i = 0; i < lists.length; i++) {
                int counter = counters[i];
                if (counter < lists[i].size()) {
                    AccountAction a = lists[i].get(counter);
                    if (a.getVersion() < version) {
                        n = i;
                    }
                }
            }
            actions.add(lists[n].get(counters[n]++));
        }
        return actions;
    }