mod = 998244353
def main():
    N = 3001
    X = 1500
    n = int(input())
    S = input()
    dp = [0 for _ in range(2*N)]
    a = 1
    for idx in range(n):
        s = S[idx]
        ndp = [0 for _ in range(2*N)]
        if s != "1":
            ndp[2] = a
        if s == "0":
            a = 0
        if s != "1":
            for i in range(-X, X+1):
                v0 = (i+1)*2
                v1 = (i-1)*2
                if -X <= v0//2 <= X:
                    ndp[v0] = (ndp[v0]+dp[i*2]) % mod
                if -X <= v0//2 <= X:
                    ndp[v1] = (ndp[v1]+dp[i*2+1]) % mod
        if s != "0":
            for i in range(-X, X+1):
                v = i*2+1
                if -X <= v//2 <= X:
                    ndp[v] = (ndp[v]+dp[i*2]+dp[i*2+1]) % mod
        dp = ndp
        #print(dp[-10:] + dp[:10])
    ans = a
    for u in range(-X, 1, 2):
        ans = (ans+dp[u*2]+dp[u*2+1]) % mod
    return ans

print(main())