N = gets.to_i
S = gets.chomp

if S[0] == S[1]
	# A-type
	a = 1
	b = 1
	(1 .. N / 2).each do |i|
		a = a * (N - i + 1) % 998244353
		b = b * i % 998244353
	end
	puts a * b.pow(998244351, 998244353) % 998244353
else
	# B-type
	puts 2.pow(N / 2, 998244353)
end