public class Solution {
    
    static Map<Integer, Integer> indexMaxValueMap = new HashMap<>();

    static int maxSubsetSum(int[] arr, int currentIndex) {
        if (currentIndex > arr.length - 1) {
            return 0;
        }
        
        if (indexMaxValueMap.get(currentIndex) != null) {
            return indexMaxValueMap.get(currentIndex);
        }
        
        int currentValue = Math.max(0, arr[currentIndex]);
        
        currentValue += Math.max(maxSubsetSum(arr, currentIndex + 2), maxSubsetSum(arr, currentIndex + 3));
        
        indexMaxValueMap.put(currentIndex, currentValue);
        
        return currentValue;
    }

    static int maxSubsetSum(int[] arr) {
        return Math.max(maxSubsetSum(arr, 0), maxSubsetSum(arr, 1));
    }