MOD = 998244353

N = int(input())
A = input()

prefix_zero = [False]*(N+1)
suffix_one = [False]*(N+2)

for i in range(1, N+1):
    prefix_zero[i] = prefix_zero[i-1] or (A[i-1] == '0')

for i in range(N, 0, -1):
    suffix_one[i] = suffix_one[i+1] or (A[i-1] == '1')

K = 0
for i in range(1, N+1):
    if prefix_zero[i] and suffix_one[i]:
        K += 1

if K == 0:
    print(1)
else:
    print((pow(2, K, MOD) - 1) % MOD)