public static int workbook(int n, int k, List<Integer> arr) {
// Write your code here
     Map<Integer, List<Integer>> bookMap = new HashMap<>();
    int pageNr = 1;

    for (int i = 0; i < n; i++) {
        List<Integer> problemsPerPage = new ArrayList<>();
        for (int j = 0; j < arr.get(i); j++) {
            if (problemsPerPage.size() == k) {
                bookMap.put(pageNr, problemsPerPage);
                pageNr++;
                problemsPerPage = new ArrayList<>();
            }
            problemsPerPage.add(j + 1);
        }
        bookMap.put(pageNr, problemsPerPage);
        pageNr++;
    }
    AtomicInteger specialProblems = new AtomicInteger();
    bookMap.keySet().forEach(key -> {
        if (bookMap.get(key).contains(key)) {
            specialProblems.getAndIncrement();
        }
    });

    return specialProblems.get();
}