public static int beautifulTriplets(int d, List<Integer> arr) {
    // Write your code here
     int triplets=0;
     for(int i=0;i<arr.size();i++){
         int sum = d+arr.get(i);
         if(arr.contains(sum)){
            sum=sum+d;
            if(arr.contains(sum)){
                triplets++;
            }
         }
    }
        return triplets;
     }