function workbook(n: number, k: number, arr: number[]): number {
  let counter = 0;

  let page = 1;
  let chapter = 1;
  let problem = 1;
  while (chapter <= n) {
    const ps = Array(Math.min(problem + k - 1, arr[chapter - 1]) - problem + 1)
      .fill(0)
      .map((_, i) => i + problem);

    if (problem > arr[chapter - 1]) {
      chapter++;
      problem = 1;
      continue;
    }

    if (ps.includes(page)) counter++;

    page++;
    problem = ps[ps.length - 1] + 1;
    continue;
  }

  return counter;
}