## Hackerrank - Lisa's Workbook Solution

Lisa just got a new math workbook. A workbook contains exercise problems, grouped into chapters. Lisa believes a problem to be *special* if its index (within a chapter) is the same as the page number where it's located. The format of Lisa's book is as follows:

- There are chapters in Lisa's workbook, numbered from to .
- The chapter has problems, numbered from to .
- Each page can hold
*up to*problems. Only a chapter's last page of exercises may contain fewer than problems. - Each new chapter starts on a new page, so a page
*will never*contain problems from more than one chapter. - The page number indexing starts at .

Given the details for Lisa's workbook, can you count its number of *special* problems?

For example, Lisa's workbook contains problems for chapter , and problems for chapter . Each page can hold problems. The first page will hold problems for chapter . Problem is on page , so it is *special*. Page contains only Chapter , Problem , so no *special* problem is on page . Chapter problems start on page and there are problems. Since there is no problem on page , there is no *special* problem on that page either. There is *special* problem in her workbook.

** Note:** See the diagram in the

*Explanation*section for more details.

**Function Description**

Complete the *workbook* function in the editor below. It should return an integer that represents the number of special problems in the workbook.

workbook has the following parameter(s):

*n*: an integer that denotes the number of chapters*k*: an integer that denotes the maximum number of problems per page*arr*: an array of integers that denote the number of problems in each chapter

**Input Format**

The first line contains two integers and , the number of chapters and the maximum number of problems per page.

The second line contains space-separated integers where denotes the number of problems in the chapter.

**Constraints**

**Output Format**

Print the number of *special* problems in Lisa's workbook.

**Sample Input**

```
5 3
4 2 6 1 10
```

**Sample Output**

```
4
```

**Explanation**

The diagram below depicts Lisa's workbook with chapters and a maximum of problems per page. Special problems are outlined in red, and page numbers are in yellow squares.

There are special problems and thus we print the number on a new line.

### Solution in Python

```
from math import ceil
def workbook(n, k, arr):
p,c = 1,0
for i in arr:
for j in range(ceil(i/k)):
if p>j*k and p<=j*k+min(k,i):
c+=1
i-=k
p+=1
return c
n,k = map(int,input().split())
arr = map(int,input().split())
print(workbook(n, k, arr))
```