from itertools import zip_longest
N=int(input())
A=tuple(map(int,input().split()))
MOD=998244353
dp=[[0 for i in range(A[0]+1)]]+[[0 for j in range(A[i]+1)]for i in range(N)]
dp[0][0] = 1
for i in range(len(dp)):
  for j in range(len(dp[i])):
    if i==0:
      dp[i][j] += dp[i][j-1]
    elif j==0:
      dp[i][j] += dp[i-1][j]
    else:
      dp[i][j] += dp[i-1][j] + dp[i][j-1]
    dp[i][j] %= MOD

ans = 0

dp=list(zip_longest(*dp))

for i in range(len(dp)):
  flag = False
  for j in range(len(dp[i])-1, -1, -1):
    if dp[i][j]!=None:
      if flag:
        ans += dp[i][j]
        break
      else:
        flag = True

print(ans)