#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Comb
{
  std::vector<long long> fac, finv, inv;
  const int mod;
  Comb(const int max, const int m) : mod(m), fac(max + 5), finv(max + 5), inv(max + 5)
  {
    fac[0] = fac[1] = finv[0] = finv[1] = inv[1] = 1;
    for (int i = 2; i < max + 5; ++i)
    {
      fac[i] = fac[i - 1] * i % mod;
      inv[i] = mod - inv[mod % i] * (mod / i) % mod;
      finv[i] = finv[i - 1] * inv[i] % mod;
    }
  }
  long long c(int n, int k)
  {
    if (n < k || n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % mod) % mod;
  }
  long long p(int n, int k)
  {
    if (n < k || n < 0 || k < 0) return 0;
    return fac[n] * finv[n - k] % mod;
  }
};

int main()
{
	const int ma = 2e5 + 5;
	int n;
	cin >> n;
	const int mod = 998244353;
	Comb cb(ma, mod);
	vector<int> a(n);
	for (int i = 0; i < n; ++i) cin >> a[i];
	int now = a[0];
	long long ans = 1;
	for (int i = 0; i < n; ++i)
	{
		ans = (ans + cb.c(i + a[i], i + 1)) % mod;
	}
	cout << ans << endl;
}