import sys
input = sys.stdin.readline

mod = 998244353
N = int(input())
S = input().rstrip()
allone = [True] * (N+1)
for i in range(N)[::-1]:
    allone[i] = allone[i+1] and (S[i] in '1?')

ans = 0
if allone[0]:
    ans = 1

dp0 = [0] * (3*N+1)
dp1 = [0] * (3*N+1)
dp1[0] = 1

for i in range(N):
    ndp0 = [0] * (3*N+1)
    ndp1 = [0] * (3*N+1)
    if S[i] != '0':
        for j in range(-2*N, N+1):
            if j-2 >= -2*N:
                ndp1[j-2] = (ndp1[j-2] + dp0[j]) % mod
            ndp1[j] = (ndp1[j] + dp1[j]) % mod
    if S[i] != '1':
        for j in range(-2*N, N):
            ndp0[j+1] = (ndp0[j+1] + dp0[j] + dp1[j]) % mod
    dp0 = ndp0
    dp1 = ndp1

    if allone[i+1]:
        for i in range(-2*N, 1, 2):
            ans = (ans + dp0[i]) % mod
print(ans)