def invoice_total(items, discount_percent=0):
    if not isinstance(discount_percent, int) or not 0 <= discount_percent <= 100:
        raise ValueError("Discount must be an integer from 0 to 100")
    subtotal = 0
    for item in items:
        price, quantity = item["unit_cents"], item["quantity"]
        if not isinstance(price, int) or not isinstance(quantity, int) or price < 0 or quantity < 0:
            raise ValueError("Price and quantity must be nonnegative integers")
        subtotal += price * quantity
    return (subtotal * (100 - discount_percent) + 50) // 100