#include <stdio.h>
#include <string.h>

#define MOD 998244353
#define MAXN 500005

int N;
char A[MAXN];
int has1_suffix[MAXN];
int has0_prefix[MAXN];

int main() {
    scanf("%d", &N);
    scanf("%s", A + 1);

    // suffix: can become 1
    has1_suffix[N+1] = 0;
    for (int i = N; i >= 1; i--) {
        has1_suffix[i] = has1_suffix[i+1] || (A[i] == '1');
    }

    // prefix: can become 0
    has0_prefix[0] = 0;
    for (int i = 1; i <= N; i++) {
        has0_prefix[i] = has0_prefix[i-1] || (A[i] == '0');
    }

    long long ans = 0;

    for (int k = 0; k <= N; k++) {
        int ok = 1;

        if (k > 0) {
            if (!has1_suffix[k]) ok = 0;
        }

        if (k < N) {
            if (!has0_prefix[k+1]) ok = 0;
        }

        if (ok) ans++;
    }

    printf("%lld\n", ans % MOD);
    return 0;
}