public static int calcTriplets(int [] arr, int n){
        int count = 0;
        for (int itr = 0; itr < arr.length-2; itr++){
            int start = itr + 1;
            int end = arr.length-1;
            while (start < end){
                while ((start < end) && (arr[itr] + arr[start] + arr[end] > n)){
                    end--;
                }

                while ((start < end) && (arr[itr] + arr[start] + arr[end] <= n)){
                    count++;
                    start++;
                }
            }
        }

        return count;
    }