#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll const m = 998244353;
int main () {
	int N;
	cin >> N;
	ll ans = 1;
	ll pre = -1;
	for (int i = 0; i < N; i ++) {
		char c;
		cin >> c;
		if (c == '1') {
			if (pre >= 0) {
				ans = (ans * (i - pre + 1)) % m;
			}
			pre = i;
		}
	}
	if (pre < 0) ans = 0;
	cout << ans << endl;
}