n=int(input())
A=list(map(int,input().split()))
A+=[0]
p=998244353
def kaimod(n,p):
  l=[1]
  a=1
  for i in range(1,n+1):
    a=(a*i)%p
    l+=[a]
  b=pow(a,p-2,p)
  ll=[1]*(n+1)
  ll[n]=b
  for i in range(n-1,1,-1):
    b=(b*(i+1))%p
    ll[i]=b
  return([l,ll])
q=kaimod(A[0]+n,p)
kai=q[0]
kair=q[1]
def binom(n,m):
  return((((kai[n+m]*kair[m])%p)*kair[n])%p)
ans=1
x=A[0]+1
for i in range(1,n+1):
  if A[i-1]>A[i]:
    x-=1
    ans=(ans+binom(x-1,i-1))%p
  while x>=A[i]+2:
    x-=1
    ans=(ans+binom(x-1,i-1))%p
  if i!=n:
     ans=(ans+binom(x-2,i))%p
print(ans)