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;
}

def workbook(n, k, arr):
    sp = 0
    page = 0
    
    for i in range(n):
        page += 1
        
        for j in range(1, arr[i]+1):
            if (j == page):
                sp += 1
            if (j % k == 0 and j!=arr[i]):
                page += 1
    
    return sp

n, k = map(int, input().split())
arr = list(map(int, input().split()))

result = workbook(n, k, arr)

print(result)

function workbook($n, $k, $arr) {
    $result = array_fill(0, array_sum($arr), []);
    $pages = 0;
    $specials = 0;

    foreach ($arr as $numPages) {
        for ($problem = 1; $problem <= $numPages; $problem++) {
            if (count($result[$pages]) >= $k || $problem === 1) {
                $pages++;
            }
            $result[$pages][] = $problem;
        }
    }

    for ($i = 1; $i < count($result); $i++) {
        if (in_array($i, $result[$i])) {
            $specials++;
        }
    }

    return $result;
}

int workbook(int n, int k, vector<int> arr) {
    int page = 1, chapter = 1, fe = 1, res = 0;
    while(chapter <= arr.size()){
        int le = min(fe + k - 1, arr[chapter-1]);
        if(fe <= page && page <= le) res++;
        fe = le + 1;
        if(fe > arr[chapter-1]) {
            chapter++;
            fe = 1;
        }
        page ++;
    }   
    return res;
}

public static int workbook(int n, int k, List<Integer> arr) {
        int pages = 0;
        int result = 0;
        for (int chapter : arr) {
            pages++;
            for (int i = 1; i <= chapter; i++) {
                if (pages == i) {
                    result++;
                }
                if (i % k == 0 && i < chapter) {
                    pages++;
                }
            }
        }
        return result;
    }