# So Easy!

Time Limit: 2000/1000 MS (Java/Others)

Memory Limit: 32768/32768 K (Java/Others)

## Description

A sequence Sn is defined as:

Where a, b, n, m are positive integers.┌x┐is the ceil of x. For example, ┌3.14┐=4. You are to calculate Sn.
You, a top coder, say: So easy!

## Input

There are several test cases, each test case in one line contains four positive integers: a, b, n, m. Where 0< a, m < 215, (a-1)2< b < a2, 0 < b, n < 231.The input will finish with the end of file.

## Output

For each the case, output an integer Sn.

## Sample Input

2 3 1 2013
2 3 2 2013
2 2 1 2013

## Sample Output

4
14
4

zhoujiaqi2010

## Source

2013 ACM-ICPC长沙赛区全国邀请赛——题目重现