Competitions

# Linked List practice

# LinkedList Simulate Sum of Odd Elements

An empty Linked List is given initially. Simulate the next operations:

**push front x**: add element**x**to the front of a Linked List;**push back x**: add element**x**to the back of a Linked List;**pop front**: remove element from the front of a Linked List;**pop back**: remove element from the back of a Linked List;

Let **L** = (`a`

, _{1}`a`

, ...., _{2}`a`

) be the resulting Linked List. Find the sum of all its odd elements._{n}

#### Input

Each line contains one of the operations described above. It is known that **x** is a nonnegative integer, no more than **1000**. Final Linked List (after simulation) contains no more than **1000** elements.

#### Output

Print the sum of all odd elements of the resulting Linked List.

#### Example

After simulation the list will have the next form:

The sum of odd elements is **5** + **1** = **6**.

Input example #1

push back 7 push back 5 pop front push front 2 push back 1

Output example #1

6