MOD = 998244353
N, K = map(int, input().split())
S = input()
l = 0
while S[l] == '(':
	l += 1
r = K - 1;
while S[r] == ')':
	r -= 1
if l > r:
	ans = pow(2, N, MOD)
	A = 1; B = 1
	for k in range(K):
		ans = (ans - A * pow(B, -1, MOD)) % MOD
		A = A * ((N - k) % MOD) % MOD
		B = B * (k + 1) % MOD
	print(ans)
else:
	A = 1; B = 1
	for k in range(K - (r - l)):
		A = A * ((N - (r - l) - k) % MOD) % MOD
		B = B * (k + 1) % MOD
	print(A * pow(B, -1, MOD) % MOD)