Problem
Lisa just got a new math workbook. A workbook contains exercise problems, grouped into chapters.
- There are n chapters in Lisa’s workbook, numbered from 1 to n.
- The i-th chapter has ti problems, numbered from 1 to ti.
- Each page can hold up to k problems. There are no empty pages or unnecessary spaces, so only the last page of a chapter may contain fewer than k 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 1.
Lisa believes a problem to be special if its index (within a chapter) is the same as the page number where it’s located. Given the details for Lisa’s workbook, can you count its number of special problems?
Note: See the diagram in the Explanation section for more details.
Input Format
The first line contains two integers n and k — the number of chapters and the maximum number of problems per page respectively.
The second line contains n integers t1,t2,…,tn where ti denotes the number of problems in the ii-th chapter.
Constraints
- 1≤n,k,ti≤100
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 n=5 chapters and a maximum of k=3 problems per page. Special problems are outlined in red, and page numbers are in yellow squares.
There are 4 special problems and thus we print the number 4 on a new line.