Sum a Linked List

You are given a linked list node at addr HEAD. Each list node consists of a word next that points to the next node in the list, followed by a word value. The last node in the list has its next pointer set to 0 (NULL).

You can think of each node as being equivalent to the following C struct:

struct node {
    struct node *next;
    int          value;

Your task is to find the sum of all the values in the list, and write this sum to SUM, then call the break instruction