import java.math.BigInteger;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		sc.close();

		int mod = 998244353;
		Kaijou kai = new Kaijou(1000000, mod);
		long ans = 1;
		for (int i = 0; i < n; i++) {
			ans += kai.comb(a[i] + i, i + 1);
			ans %= mod;
		}
		System.out.println(ans);
	}

	static class Kaijou {
		long[] p, pi;
		int m;

		public Kaijou(int n, int mod) {
			n++;
			m = mod;
			p = new long[n];
			pi = new long[n];
			p[0] = 1;
			pi[0] = 1;
			for (int i = 1; i < n; i++) {
				p[i] = p[i - 1] * i % m;
			}
			pi[n - 1] = BigInteger.valueOf(p[n - 1])
					.modInverse(BigInteger.valueOf(m)).longValue();
			for (int i = n - 1; i > 1; i--) {
				pi[i - 1] = pi[i] * i % m;
			}
		}

		public long comb(int n, int r) {
			if (n < r) return 0;
			return p[n] * pi[r] % m * pi[n - r] % m;
		}

		public long perm(int n, int r) {
			if (n < r) return 0;
			return p[n] * pi[n - r] % m;
		}
	}
}