// Problem: No.2792 Security Cameras on Young Diagram
// Group: yukicoder
// URL: https://yukicoder.me/problems/no/2792
// Memory Limit: 512 MB
// Time Limit: 2000 ms
// Author: lingfunny
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
using namespace std;

const int mxn = 1e5 + 10, N = 1e5 + 2;
const int mod = 998244353;

int n, a[mxn], ans, fct[mxn * 2], ift[mxn * 2];

int S(int x) {
	return 1ll * x * (x + 1) / 2 % mod;
}

int qpow(int x, int k) {
	int res = 1;
	while (k) {
		if (k & 1) res = 1ll * res * x % mod;
		k >>= 1, x = 1ll * x * x % mod;
	}
	return res;
}

int C(int n, int m) {
	return 1ll * fct[n] * ift[m] % mod * ift[n - m] % mod;
}

int main() {
	scanf("%d", &n);
	for (int i = 1; i <= n; ++i) scanf("%d", a + i);
	fct[0] = 1;
	for (int i = 1; i <= N * 2; ++i) fct[i] = 1ll * fct[i - 1] * i % mod;
	ift[N * 2] = qpow(fct[N * 2], mod - 2);
	for (int i = N * 2 - 1; ~i; --i) ift[i] = 1ll * ift[i + 1] * (i + 1) % mod;
	ans = a[1] + 1;
	for (int i = 2; i <= n; ++i) {
		// a[i] >= x[i] >= x[i - 1] >= ... >= x[1] >= 1
		// a[i] + i >= x[i] + i > x[i - 1] + i -1 > .. > x[1] + 1 >= 2
		ans += C(a[i] + i - 1, i);
		// printf("ans += %d\n", C(a[i] + i - 1, i));
		ans %= mod;
	}
	printf("%d\n", ans);
	return 0;
}