#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef struct node
{
      int value;
      struct node *next;
} Node;
typedef struct stack
{
      Node *head;
      Node *tail;
} Stack;
Node *makeNode(int value)
{
      Node *p = (Node *)malloc(sizeof(Node));
      p->value = value;
      p->next = NULL;
      return p;
}
void printfnode(Node *p)
{
      if (p == NULL)
            return;
      printf("%d\n", p->value);
}
int topStack(Stack *s)
{
      if (s->tail == NULL)
            return -1;
      return s->tail->value;
}
Stack *makeStack()
{
      Stack *s;
      s = (Stack *)malloc(sizeof(Stack));
      s->head = NULL;
      s->tail = NULL;
      return s;
}
void popStack(Stack *s)
{
      Node *iterator;
      if (s->tail == NULL)
      {
            printf("ERROR STACK");
            return;
      }
      if (s->head == s->tail)
      {
            s->head = NULL;
            s->tail = NULL;
            return;
      }
      iterator = s->head;
      while (iterator->next != s->tail)
      {
            iterator = iterator->next;
      }
      iterator->next = NULL;
      s->tail = iterator;
      return;
}
void pushStack(Stack *s, int value)
{
      Node *newNode = makeNode(value);
      if (s->head == NULL)
      {
            s->head = newNode;
            s->tail = newNode;
            return;
      }
      s->tail->next = newNode;
      s->tail = newNode;
      return;
}
int n;
int main()
{
      Node node;
      int i, j;
      int total = 0;
      int cho = 0;
      int array1[1000];
      int array2[1000];
      Stack *s = makeStack();
      FILE *f = fopen("expreval.txt", "r");
      if (f == NULL)
            printf("FILE ERROR\n");
      else
      {
            fscanf(f, "%d", &n);
            for (i = 1; i <= n; i++)
            {
                  fscanf(f, "%d", &array1[i]);
            }
            for (j = 1; j < n; j++)
            {
                  fscanf(f, "%d", &array2[j]);
            }
      }
      for (i = 1; i <= n; i++)
            for (j = 1; j < n; j++)
            {
                  pushStack(s, array1[i]);
                 if(array2[j] == 2)
                 {
                       cho = topStack(s);
                       popStack(s);
                       cho = cho*array1[i];
                       pushStack(s, cho);
                 }
            }
      for(j = n-1; j >= 1; j--)
      {
            if(array2[j] == 0)
            total = total + topStack(s);
            if(array2[j] == 1)
            total = total - topStack(s);
            if(array2[j] == 2)
            total = total + topStack(s);
      }
      printf("%d\n", total);
      return 0;
}