N = int(input())
A = input()
MOD = 998244353

dp = [1, 0, 0, 0]
for c in A:
    nxt = [0] * 4
    for s in range(4):
        if not dp[s]: continue
        L, R = s // 2, s % 2
        if not (c == '1' and not R):
            ns = L * 2 | (R or c == '0')
            nxt[ns] = (nxt[ns] + dp[s]) % MOD
        if not (c == '0' and not L):
            ns = (L or c == '1') * 2 | R
            nxt[ns] = (nxt[ns] + dp[s]) % MOD
    dp = nxt

print(sum(dp) % MOD)