public int MaxBlockMult3() {
		return MaxBlockMult3(0, num.length-1);
	}
	private int MaxBlockMult3(int left, int right){
		int rtn, maxRight, maxLeft, max;
		if(left > right) 
			rtn = -1;
		else if (left == right) //one element array
			rtn = num[left];
		else {
		  int mid = (left + right)/2; 
		  int sum = 0;
		  int maxSumRight[] ;
		  maxSumRight = new int[3]; //array to store sums
		  maxSumRight[0] = 0; //sums that have modulo 0
		  maxSumRight[1] = 0; //sums that have modulo 1
		  maxSumRight[2] = 0; //sums that have modulo 2
//		add the sums of each modulo  on the right side
		  for (int i = mid + 1; i <= right; i++){
			  sum += num[i]; 
			  if (sum % 3 == 0  && sum > maxSumRight[0]) 
				  maxSumRight[0] = sum;
			  else if (sum % 3  == 1 || sum % 3 + 3 == 1 && sum > maxSumRight[1])
				  maxSumRight[1] = sum;
			  else if (sum % 3 == 2 || sum % 3 +3 == 2 && sum > maxSumRight[2])
				  maxSumRight[2] = sum;
		  }
		  sum = 0; //reset the sum value
		  int maxSumLeft[] ;
		  maxSumLeft = new int[3]; //array to store sums
		  maxSumLeft[0] = 0; //sums that have modulo 0
		  maxSumLeft[1] = 0; //sums that have modulo 1
		  maxSumLeft[2] = 0; //sums that have modulo 2
		  //add the sums of each modulo  on the left side
		  for (int i = left; i <= mid; i++){
			  sum += num[i];
			  if (sum % 3 == 0 && sum > maxSumLeft[0])
				  maxSumLeft[0] = sum;
			  else if (sum % 3 == 1 || sum % 3 + 3 == 1 && sum > maxSumLeft[1])
				  maxSumLeft[1] = sum;
			  else if (sum % 3 == 2 || sum % 3 + 3 == 2 && sum > maxSumLeft[2])
				  maxSumLeft[2] = sum;
		}
		  //recursive calls to right and left
		  maxRight = MaxBlockMult3(mid+1,right );
		  maxLeft = MaxBlockMult3(left, mid);
		  // find the maximum block from right and left return
		  if (maxRight > maxLeft)
			  max = maxRight;
			  else 
				  max = maxLeft;
		  if (maxSumRight[0]+maxSumLeft[0] > max )
			  max = maxSumRight[0]+maxSumLeft[0];
		  else if (maxSumRight[1]+maxSumLeft[2] > max)
			  max = maxSumRight[1]+maxSumLeft[2];
		  else if (maxSumRight[2]+maxSumLeft[1] > max)
			  max = maxSumRight[2]+maxSumLeft[1] ;
		  
		 // checks to make sure the max is a multiple of 3 before returning
		  if (max % 3 == 0) 
				 rtn = max;
				 else  // return -1 if there are no multiple blocks of 3
					 rtn = -1; 
				    
	}
			return rtn;
	}