Chef and Queries

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As part of his daily job, Chef has to solve problems involving sets. Till now, Chef has been using inefficient methods to solve his set related problem, wasting a lot of his precious time. He has agreed to pay you a lot of money for solving the following problem for him efficiently.
First, Chef needs to perform Q operations on a set. Each operation is either:
 1. Add a number to the set (if this number is NOT already present in the set).
 2. Erase a number from the set (if this number exists in the set).
Then, he needs to find the sum of all elements of the set after performing these Q queries. Your job is to find this sum for him quickly.
Input
The first line of input contains four integers — Q, S_{1}, A, B. S_{1} is the first number in the operations. A and B are special constants explained later.Every operation S_{i} is represented by a single integer. If S_{i} is odd, then it represents the first operation, otherwise the second type, and in both of them the integer you have to add/delete equals [S_{i} / 2], where [] is the greatest integer (or floor) function.
S_{i} = (A*S_{i1} + B) mod 2^{32} when i > 1.
Note: In this problem, the time limit is very tight. Using builtin data structures, such as set/unordered_set in C++ or TreeSet/HashSet in Java, may lead to a Time Limit Exceed verdict.
Output
Output a single line containing a single integer — sum of elements in the set after Q queries.Constraints
 1 ≤ Q ≤ 10^{7}
 1 ≤ S_{1}, A, B ≤ 10^{9}
Example
Input: 5 1 1 1 Output: 3 Input: 10000000 777777777 777777777 777777777 Output: 5362358669068782
Explanation:
The sequence {S_{i}} is 1, 2, 3, 4, 5:
Operation 1, 1 mod 2 = 1, add number [1 / 2] = 0 to set, sum is 0.
Operation 2, 2 mod 2 = 0, erase number [2 / 2] = 1 from set, 1 is not in set, so nothing happens, sum is 0.
Operation 3, 3 mod 2 = 1, add number [3 / 2] = 1 to set, sum is 1.
Operation 4, 4 mod 2 = 0, erase number [4 / 2] = 2 from set, 2 is not in set, so nothing happens, sum is 1.
Operation 5, 5 mod 2 = 1, add number [5 / 2] = 2 to set, sum is 3.
Author:  mgch 
Editorial  http://discuss.codechef.com/problems/CHEFQUE 
Tags  bitset, cook65, easymedium, hashing, mgch 
Date Added:  9122015 
Time Limit:  2 sec 
Source Limit:  50000 Bytes 
Languages:  C, CPP14, JAVA, PYTH, PYTH 3.6, PYP3 
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