#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef int64_t lint;
#define rep(i, n) for(int i=0; i<n; i++)
#define repx(i, l, n) for(int i=l; i<n; i++)
#define all(v) v.begin(), v.end()
#define show(x) cout << #x << ": " << x << endl;
#define list(x) cout << #x << ": " << x << "  ";
#define pb push_back
using vi = vector<lint>;
using vvi = vector<vector<lint>>;
template<class T> inline void vin(vector<T>& v) { rep(i, v.size()) cin >> v.at(i); }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<class T> inline void drop(T x) { cout << x << endl; exit(0); }
template<class T> void vout(vector<T> v) { rep(i, v.size()) { cout << v.at(i) << ' '; } cout << endl; }
constexpr lint LINF = LLONG_MAX/2;
using mint = modint998244353;
using vm = vector<mint>;

int main() {
	lint N;
	cin >> N;
	vi v(N);
	vin(v);

	mint a=1, b=0, c=0;
	lint x, y, z;
	v.pb(0);
	vm fact(N + v[0]), rev(N + v[0]);
	fact[0] = 1;
	rev[0] = 1;
	repx(i, 1, N + v[0]) {
		a *= i;
		fact[i] = a;
		rev[i] = (mint)1/fact[i];
	}
	rep(i, N) {
		b += fact[v[i]-1+i] * rev[v[i]-1] * rev[i];
		for (int j = v[i]-1; j >= v[i+1]; j--) {
			b += fact[j+i] * rev[j] * rev[i];
		}
	}
	std::cout << b.val() << '\n';
}