Utkarsh and Tiresome RMQ
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## Algorithms, Algorithms, Sqrt-Decomposition

Problem
Editorial
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Utkarsh loves finding maximum integers in a given sequence. But this love is not always accompanied with proper knowledge. His teacher once gave him a homework problem and due to his poor knowledge he was not able to solve it. Its 6 in the morning and he has just 2 hours left to solve the problem. Can you help him solve the problem.

He was given an array A consisting of N integers and integers B and M. He had to answer Q queries. Each query is of the form
$x\space y$ : Print the maximum integer among {$A_x +B,\space A_{x-y} +2B, \space A_{x-2y} +3B,..., \space A_{x-(M-1)y} +MB$}

$INPUT$
First line contains four integers $N, Q, B, M$.
Second line contains N integers of array A.
Next Q lines describe Q queries in the form $x\space y$.

$OUTPUT$
Print the answer to each query.

$CONSTRAINTS$
$1 ≤ N,Q,M ≤ 10^5$
$-10^9 ≤ A_i\space, B ≤ 10^9$
$1 ≤ x,y ≤N$

Note: Array A is 1-indexed. Do not consider elements in the list if corresponding index in array is non-positive, i.e., do not consider $A_{x - (i-1)\times y} + iB$ if $(x - (i-1)\times y) ≤ 0$

SAMPLE INPUT
8 8 3 3
4 8 7 4 1 10 1 12
1 1
2 1
3 1
4 2
5 3
6 1
7 2
8 1
SAMPLE OUTPUT
7
11
14
14
14
13
16
19

Explanation

The list of integers for each query: maximum

1. {4+3} : 7
2. {8+3, 4+6}: 11
3. {7+3, 8+6, 4+9}:14
4. {4+3, 8+6}: 14
5. {1+3, 8+6}: 14
6. {10+3, 1+6, 4+9}: 13
7. {1+3, 1+6, 7+9} : 16
8. {12+3, 1+6, 10+9}: 19

(Note that in some lists less than three elements are considered because their corresponding array index is non positive)

Time Limit: 2,0 sec(s) for each input file.
Memory Limit: 512 MB
Source Limit: 1024 KB

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