n=int(input())
M=998244353
fa=[1,1]
fb=[1,1]
for i in range(2,200001):
  fa+=[fa[-1]*i%M]
  fb+=[fb[-1]*(M//i)*fb[M%i]*fa[M%i-1]*(-1)%M]
a=list(map(int,input().split()))+[0]
a.reverse()
g=1
w=0
for i in range(n):
  for j in range(1,a[i+1]-a[i]+1):
    w+=1
    g+=fa[n-i-1+w]*fb[n-i-1]*fb[w]
    g%=M
print(g)