#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct node {
  struct node *next;
  int data;
};

int product(struct node *head1, struct node *head2);
struct node *strings_to_list(int len, char *strings[]);

// DO NOT CHANGE THIS MAIN FUNCTION
int main(int argc, char *argv[]) {
  // create two linked lists from command line arguments
  int dash_arg = argc - 1;
  while (dash_arg > 0 && strcmp(argv[dash_arg], "-") != 0) {
    dash_arg = dash_arg - 1;
  }
  struct node *head1 = strings_to_list(dash_arg - 1, &argv[1]);
  struct node *head2 =
      strings_to_list(argc - dash_arg - 1, &argv[dash_arg + 1]);

  int result = product(head1, head2);
  printf("%d\n", result);

  return 0;
}

// product should return the sum of the elements in list1 multiplied by
// the corresponding element in list2
// if one list is longer than the other, the extra list elements are ignored
int product(struct node *head1, struct node *head2) {
  struct node *current1 = head1;
  struct node *current2 = head2;

  int result = 0;

  while ((current1 != NULL) && (current2 != NULL)) {
    result += (current1->data) * (current2->data);
    current1 = current1->next;
    current2 = current2->next;
  }
  return result;
}

// DO NOT CHANGE THIS FUNCTION
// create linked list from array of strings
struct node *strings_to_list(int len, char *strings[]) {
  struct node *head = NULL;
  for (int i = len - 1; i >= 0; i = i - 1) {
    struct node *n = malloc(sizeof(struct node));
    assert(n != NULL);
    n->next = head;
    n->data = atoi(strings[i]);
    head = n;
  }
  return head;
}