public class Main {
    public static void main(String[] args) {
        int[] arr = {3, 2, 7, 10, 12, 15};
        int n = arr.length;
 
        if (n == 0) {
            System.out.println(0);
            return;
        }
 
        if (n == 1) {
            System.out.println(arr[0]);
            return;
        }
 
        int prev2 = 0, prev1 = arr[0];
 
        for (int i = 1; i < n; i++) {
            int take = arr[i] + prev2;
            int skip = prev1;
            int current = Math.max(take, skip);
 
            prev2 = prev1;
            prev1 = current;
        }
 
        System.out.println(prev1);
    }
}
 

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