class Combination:

    def __init__(self, MX=10**6, MOD=998244353):
        self.MX = MX
        self.MOD = MOD
        self.fact = [1] * (MX + 1)
        self.inv = [1] * (MX + 1)
        self.f_inv = [1] * (MX + 1)
        for i in range(2, MX + 1):
            self.fact[i] = (self.fact[i - 1] * i) % self.MOD
            self.inv[i] = ( - (self.MOD // i) * (self.inv[self.MOD % i])) % self.MOD
            self.f_inv[i] = (self.f_inv[i - 1] * self.inv[i]) % self.MOD
    
    def invs(self, n):
        if n <= self.MX:
            return self.inv[n]
        else:
            return pow(n, self.MOD - 2, self.MOD)
    
    def p(self, n, r):
        if r > n or r < 0:
            return 0
        return (self.fact[n] * self.f_inv[r]) % self.MOD
    
    def c(self, n, r):
        if r > n or r < 0:
            return 0
        return (self.fact[n] * self.f_inv[r] * self.f_inv[n - r]) % self.MOD


MOD = 998244353
com = Combination()
N = int(input())
A = list(map(int, input().split()))

ans = 1
ans %= MOD
for i in range(N):
    ans += com.c(i + A[i], i + 1)
    ans %= MOD
# ans += com.c(N + A[-1], N)
ans %= MOD
print(ans)