#define _CRT_SECURE_NO_WARNINGS

#include <bits/stdc++.h>
using namespace std;

#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;

int main() {
	int n, m;
	cin >> n >> m;
	assert(1 <= n && n <= (int)1e5);
	assert(1 <= m && m <= (int)1e5);

	vector<int> a(n);
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		assert(0 <= a[i] && a[i] < 998244353);
	}

	string s;
	cin >> s;
	for (int j = 0; j < m; j++) {
		assert(s[j] == 'a' || s[j] == 's');
	}

	// g_j(x) を (1-x)^(e_1) (1-2x)^(e_2) (1-3x)^(e_3) ... と表したときの指数列を更新していく．
	deque<int> q{ -1 }; int q_sum = -1;
	for(auto c : s) {
		if (c == 's') {
			q.push_front(-q_sum - 1);
			q_sum = -1;
		}
		else if (c == 'a') {
			q.front()--;
			q_sum--;
		}
	}
	q.push_front(0);
	int K = (int)q.size();
	
	// g_M(x) の (1-kx) たちを分子と分母に振り分ける．
	vector<vector<mint>> nums{ {1} }, dnms{ {1} };
	for (int k = 1; k < K; k++) {
		if (q[k] > 0) {
			for (int tmp = 0; tmp < q[k]; tmp++) {
				nums.push_back(vector<mint>{1, -k});
			}
		}
		else if (q[k] < 0) {
			for (int tmp = 0; tmp < -q[k]; tmp++) {
				dnms.push_back(vector<mint>{1, -k});
			}
		}
	}

	// 分子を分割統治法で求める．
	int Dnum = (int)nums.size();
	for (int d = 1; d < Dnum; d *= 2) {
		for (int i = 0; i + d < Dnum; i += 2 * d) {
			nums[i] = convolution(nums[i], nums[i + d]);
		}
	}

	// 分母を分割統治法で求める．
	int Ddnm = (int)dnms.size();
	for (int d = 1; d < Ddnm; d *= 2) {
		for (int i = 0; i + d < Ddnm; i += 2 * d) {
			dnms[i] = convolution(dnms[i], dnms[i + d]);
		}
	}
	
	// 分母の形式的冪級数としての逆元を求める．
	dnms[0].resize(n);
	vector<mint> dnm_inv{ dnms[0][0].inv() };
	for (int k = 1; k < n; k *= 2) {
		int len = min(2 * k, n);
		vector<mint> tmp(len);
		int i_ub = min(len, n);
		for (int i = 0; i < i_ub; i++) tmp[i] = -dnms[0][i];
		tmp = convolution(tmp, dnm_inv);
		tmp.resize(len);
		tmp[0] += 2;
		dnm_inv = convolution(dnm_inv, tmp);
		dnm_inv.resize(len);
	}

	// g_M(x) を求める．
	auto f = convolution(nums[0], dnm_inv);

	// 答えへの寄与を足し合わせる．
	mint res;
	for (int i = 0; i < n; i++) {
		int l = i;
		int r = n - 1 - i;
		res += a[i] * f[l] * f[r];
	}

	cout << res.val() << endl;
}