public static List<Integer> icecreamParlor(int m, List<Integer> arr) {
        Map<Integer, Integer> flavorMap = new HashMap<>();
        
        for (int i = 0; i < arr.size(); i++) {
            int currentFlavorCost = arr.get(i);
            int complementCost = m - currentFlavorCost;
            
            if (flavorMap.containsKey(complementCost)) {
                return Arrays.asList(flavorMap.get(complementCost) + 1, i + 1);
            }
            
            flavorMap.put(currentFlavorCost, i);
        }
        
        return null; 
    }