MOD = 998244353
N = int(input())
S = input().strip()
if N==2:
    print(2)
else:
    A = [1]*(N+1)
    for i in range(2,N+1):
        A[i] = (A[i-1]*i)%MOD
    B = [1]*(N+1)
    B[N] = pow(A[N],MOD-2,MOD)
    for i in range(N-1,1,-1):
        B[i] = (B[i+1]*(i+1))%MOD
    def comb(n,k):
        if k<0 or k>n:return 0
        return A[n]*B[k]*B[n-k]%MOD
    if S[1]==S[0]: # A
        ans = 0
        for k in range(0,N+1,2):
            ans = (ans + comb(N//2,k//2)*comb(N//2,k//2))%MOD
    else: # B
        ans = pow(2,N//2,MOD)
    print(ans)