int workbook(int n, int k, vector<int> arr) {
    int page = 0, special = 0;
    for (int i = 0; i < n; i++) {
        int cur = 0, prev = 0; //cur -> last problem in current page. prev -> last problem in previous page.
        while(arr[i] > 0) {
            prev = cur;
            if (arr[i] > k) 
                cur += k;  //if arr[i] > k  then k no: of problems are there in current page.
            else 
                cur += arr[i]; //else only arr[i] no:of problems are there in this page.
            page++; // no: of problems are calculated and page is incremented
            if (page <= cur && page > prev) 
                special++; //if page no: lies between previous page last problem(exclusive) and current page last problem(inclusive) it is a special problem.
            arr[i] -= k;
        }
    }
    return special;
}