class CP:
    def __init__(self, N):
        self.fact = [1]
        self.fact_inv = [1]
        for i in range(1, N+1):
            self.fact.append((self.fact[-1]*i)%MOD)
            self.fact_inv.append(pow(self.fact[-1], MOD-2, MOD))
    def C(self, N, K):
        if N >= K:
            return self.fact[N]*self.fact_inv[K]%MOD*self.fact_inv[N-K]%MOD
        else:
            return 0
    def P(self, N, K):
        if N >= K:
            return self.fact[N]*self.fact_inv[N-K]%MOD
        else:
            return 0

N = int(input())
A = list(map(int, input().split()))

MOD = 998244353
cp = CP(10**5*2)
ans = 0
for i in range(N):
    ans += cp.C(A[i]+i, i+1)
    ans %= MOD

print((ans+1)%MOD)