Can some one please help me with this code , i need to divide and conquer by 3! i mean i need to split the array by 3 not by 2 , i wrote this code but it still give me error "StackOverFlow error " someone please edit it and tell me what is the problem :)

// Can some one please help me with this code , i need to divide and conquer by 3! i mean i need to split the array by 3 not by 2 , i wrote this code but it still give me error "StackOverFlow error " someone please edit it and tell me what is the problem :)

public class divided_by_three{

   // Main function that sorts arr[l..r] using
   // merge()
   void merge_sort(int arr[], int p, int r)
   {
   if (p < r)
   {
   // Find the middle point
   int q = (p+r)/3;

   // Sort first and second halves
   merge_sort(arr , p , q);
   merge_sort(arr , (q+1) , (2*q));
               merge_sort(arr , ((2*q)+1) , r);

   // Merge the sorted halves
   merge(arr, p, q, r);
   }
}

void merge(int arr[], int p, int q, int r)
{
// Find sizes of two subarrays to be merged
int n1 = q - p + 1; // n1 = 2-0+1 = 3
int n2 = (2*q) - q ;   // n2= 2*2 - 2 = 2
int n3 = r - (2*q); // 7 - 2*2 = 3

/* Create temp arrays */
int L[] = new int [n1+1]; // it will take 4 values
int M[] = new int [n2+1]; // it will take 3 values;
int R[] = new int [n3+1]; // it will take 4 values

/*Copy data to temp arrays*/
       for (int i=0; i<n1; i++)
       L[i] = arr[p + i];

       for (int i=0; i<n2; i++)
       M[i] = arr[q+1 + i];

   for (int j=0; j<n3; j++)
R[j] = arr[(2*q) + 1+ j];

       L[n1]=Integer.MAX_VALUE;
       M[n2]=Integer.MAX_VALUE;
R[n3]=Integer.MAX_VALUE;

int i = 0, j = 0 , m=0;
for(int k=p; k<=r ; k++)
{

           if (L[i] <= M[m])
           {
                   if(L[i] <= R[j])
           {
              arr[k] = L[i];
              i++;
           }
           else
           {
                       arr[k] = R[j];
                           p++;
                  }
           }
           else
           {
                           if(M[m] <= R[j])
                           {
               arr[k] = M[m];
               j++;
               }
               else
               {
                               arr[k] = R[j];
                               p++;
                           }
}
   }
}

/* A utility function to print array of size n */
static void printArray(int arr[])
{
int n = arr.length;
for (int i=0; i<n; i++)
System.out.print(arr[i] + " ");
System.out.println();
}

// Driver method
public static void main(String args[])
{
int arr[] = {5,2,4,7,1,3,2,6};

System.out.println("Given Array");
printArray(arr);

divided_by_three ob = new divided_by_three();
ob.merge_sort(arr, 0, arr.length-1);

System.out.println("\nSorted array");
printArray(arr);
}
}