Map<Integer, Integer> map = new HashMap<>();

        for (int i = 0; i < arr.size(); i++) {
            int complement = m - arr.get(i);

            if (map.containsKey(complement)) {
                return Arrays.asList(map.get(complement) + 1, i + 1);
            }

            map.put(arr.get(i),i);
        }

        return Arrays.asList(-1, -1); 
}