#include <bits/stdc++.h>


using namespace std;

template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
 void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#ifdef ONPC
  #define deb(...) cerr << '[' <<  __LINE__ << "] (" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#else
  #pragma GCC optimize("O3,unroll-loops")
  #pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
  #define deb(...)
#endif

// c++ short types
#define vt vector
//typedef long long ll;
typedef long double ld;

void whattime() { cout << "finished in " << clock() * 1.0 / CLOCKS_PER_SEC << " sec" << endl; }
// const int mod = 1e9 + 7;
const int mod = 998244353;
const int inf = 1e9;
const int64_t infll = 1e13;
bool debug = false;
const ld eps = 1e-9;
const ld pi = acos(-1);
mt19937_64 rng((int) chrono::steady_clock::now().time_since_epoch().count());

const int K = 3;

int getId(char c) {
	if(c == 'o') {
		return 0;
	} else if(c == 'k') {
		return 1;
	} else {
		assert(c == '?');
		return 2;
	}
}

struct Vertex {
	int next[K];
	bool output = false;
	int p = -1, link = -1;
	char pch;
	int go[K];

	Vertex(int p = -1, char ch = '?') : p(p), pch(ch) {
		fill(next, next + K, -1);
		fill(go, go + K, -1);
	}
};

vt<Vertex> t(1);
void add_string(const string &s) {
	int v = 0;
	for(char ch: s) {
		int c = getId(ch);
		if(t[v].next[c] == -1) {
			t[v].next[c] = t.size();
			t.emplace_back(v, ch);
		}
		v = t[v].next[c];
	}
	t[v].output = true;
}

int go(int v, char ch);

int get_link(int v) {
	if(t[v].link == -1) {
		if(v == 0 || t[v].p == 0) {
			return t[v].link = 0;
		} else {
			t[v].link = go(get_link(t[v].p), t[v].pch);
		}
	}
	return t[v].link;
}

int go(int v, char ch) {
	int c = getId(ch);
	if(t[v].go[c] == -1) {
		if(c == 2) {
			for(int i = 0; i < K; ++i) {
				t[v].go[c] = max(t[v].go[c], t[v].next[i]);
			}
		}
		if(t[v].go[c] == -1) {
			t[v].go[c] = max(t[v].next[c], t[v].next[2]);
			if(t[v].go[c] == -1) {
				t[v].go[c] = v == 0 ? 0 : go(get_link(v), ch);
			}
		}
	}
	return t[v].go[c];
}

void solve() {
	int o, k;
	cin >> o >> k;
	string s, p;
	cin >> s >> p;
	if(s.size() < p.size()) {
		cout << "0\n";
		return ;
	}
	add_string(p);
	int cost = 0;
	vt<int> dp(s.size(), 0), vertices(32, 0);
	for(int i = 0; i < int(s.size()); ++i) {
		if(i) {
			dp[i] = dp[i-1];
		}
		if(i >= p.size()) {
			if(s[i - p.size()] == 'o') {
				cost -= o;
			} else {
				cost -= k;
			}
		}
		if(s[i] == 'o') {
			cost += o;
		} else {
			cost += k;
		}
		for(int j = vertices.size() - 1; j >= 0; --j) {
			vertices[j] = go(vertices[j], s[i]);
			if(j) {
				vertices[j] = max(vertices[j], go(vertices[j-1], '?'));
			}
		}
		int z = 33;
		for(int j = 0; j < int(vertices.size()); ++j) {
			if(t[vertices[j]].output) {
				z = j;
				break;
			}
		}
		// deb(i, cost, z);
		if(i + 1 >= p.size()) {
			int value = cost >> z;
			if(i - (int)p.size() >= 0) {
				value += dp[i-p.size()];
			}
			// deb(value);
			dp[i] = max(dp[i], value);
		}
	}
	cout << dp.back() << '\n';
}


int main()
{
	// ios::sync_with_stdio(false); cin.tie(nullptr);
#ifdef ONPC
	freopen("C:\\Users\\raf4i\\CLionProjects\\cp\\inp.txt", "r", stdin);
#endif
	int tt = 1;
	if(debug) {
		tt = 1e6;
	} else {
    // cin >> tt;
	}
	for(int t = 0; t < tt; ++t) {
		solve();
	}

#ifdef ONPC
	whattime();
#endif

	return 0;
}