One weekend, there were 77 pizzas ordered for the sophomore dorm. That weekend 12 customers ordered their pizza with just pepperoni, 19 customers ordered their pizza with just sausage, 20 ordered theirs with just onions, 13 ordered theirs with pepperoni and sausage, 12 ordered theirs with sausage and onions, 11 ordered theirs with pepperoni and onions, and 7 ordered theirs with all three items. How many customers ordered their pizza with pepperoni or sausage (or both)?