public static List<Integer> icecreamParlor(int m, List<Integer> arr) {
// Write your code here
    Map<Integer, Integer> costVsIndex = new HashMap<>();
    List<Integer> result = new ArrayList<>();
    for(int i = 0; i< arr.size(); i++) {
        Integer remaining = m - arr.get(i);
        if(costVsIndex.containsKey(remaining)) {
             result.add(costVsIndex.get(remaining) + 1);
             result.add(i + 1);
        } else {
            costVsIndex.put(arr.get(i), i);
        }
    }
    return result;
}

}