import sys
import re

N = input().strip()
A = input().strip()

result = 0
dic = [A]
test = [A]
while True:
    index = [m.start() for m in re.finditer("01", test[0])]
    num = len(index)
    for i in range(num):
        target = test[0]
        target_ind = index[i]

        target_change1 = target[:target_ind] + "1" + target[target_ind+1:]
        if not(target_change1 in dic):
            dic.append(target_change1)
            test.append(target_change1)

        target_change0 = target[:target_ind+1] + "0" + target[target_ind+2:]
        if not(target_change0 in dic):
            dic.append(target_change0)
            test.append(target_change0)

    test.pop(0)
    result += 1
    if test == []:
        break

modulo = result % 998244353
print(modulo)