from collections import deque n, h0, *nlst = map(int, open(0).read().strip().split()) q = deque([[0, h0]]) res = 0 while q: cur, h = q.popleft() if cur + nlst[cur] == n - 1: res += 1 elif cur + nlst[cur] < n - 1: q.append([cur + nlst[cur], nlst[cur]]) if nlst[cur] == h: continue if cur + h == n - 1: res += 1 elif cur + h < n - 1: q.append([cur + h, h]) print(res % 998244353)