#include <iostream>
#include <vector>
#include <set>
#include <algorithm>
#include <ctime>
#include <cmath>
#include <map>
#include <assert.h>
#include <fstream>
#include <cstdlib>
#include <random>
#include <iomanip>

using namespace std;

#define sqr(a) ((a)*(a))
#define all(a) (a).begin(), (a).end()

const long long MOD = (long long) 1e9 + 7;
const long long MAX_N = (long long) 100;

long long binPow(long long a, long long b) {
    if (b == 0)
        return 1;

    long long ans = binPow(a, b / 2);
    ans = ans * ans % MOD;

    if (b % 2)
        ans = ans * a % MOD;

    return ans;
}

// make it understandable one day...
namespace fft {

typedef double dbl;

struct num {
  dbl x, y;
  num() { x = y = 0; }
  num(dbl x_, dbl y_) : x(x_), y(y_) {}
};

inline num operator+(num a, num b) { return num(a.x + b.x, a.y + b.y); }
inline num operator-(num a, num b) { return num(a.x - b.x, a.y - b.y); }
inline num operator*(num a, num b) { return num(a.x * b.x - a.y * b.y, a.x * b.y + a.y * b.x); }
inline num conj(num a) { return num(a.x, -a.y); }

int base = 1;
vector<num> roots = {{0, 0}, {1, 0}};
vector<int> rev = {0, 1};

const dbl PI = static_cast<dbl>(acosl(-1.0));

void ensure_base(int nbase) {
  if (nbase <= base) {
    return;
  }
  rev.resize(1 << nbase);
  for (int i = 0; i < (1 << nbase); i++) {
    rev[i] = (rev[i >> 1] >> 1) + ((i & 1) << (nbase - 1));
  }
  roots.resize(1 << nbase);
  while (base < nbase) {
    dbl angle = 2 * PI / (1 << (base + 1));
//      num z(cos(angle), sin(angle));
    for (int i = 1 << (base - 1); i < (1 << base); i++) {
      roots[i << 1] = roots[i];
//        roots[(i << 1) + 1] = roots[i] * z;
      dbl angle_i = angle * (2 * i + 1 - (1 << base));
      roots[(i << 1) + 1] = num(cos(angle_i), sin(angle_i));
    }
    base++;
  }
}

void fft(vector<num>& a, int n = -1) {
  if (n == -1) {
    n = (int) a.size();
  }
  assert((n & (n - 1)) == 0);
  int zeros = __builtin_ctz(n);
  ensure_base(zeros);
  int shift = base - zeros;
  for (int i = 0; i < n; i++) {
    if (i < (rev[i] >> shift)) {
      swap(a[i], a[rev[i] >> shift]);
    }
  }
  for (int k = 1; k < n; k <<= 1) {
    for (int i = 0; i < n; i += 2 * k) {
      for (int j = 0; j < k; j++) {
        num z = a[i + j + k] * roots[j + k];
        a[i + j + k] = a[i + j] - z;
        a[i + j] = a[i + j] + z;
      }
    }
  }
}

vector<num> fa, fb;

vector<int64_t> square(const vector<int>& a) {
  if (a.empty()) {
    return {};
  }
  int need = (int) a.size() + (int) a.size() - 1;
  int nbase = 1;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  int sz = 1 << nbase;
  if ((sz >> 1) > (int) fa.size()) {
    fa.resize(sz >> 1);
  }
  for (int i = 0; i < (sz >> 1); i++) {
    int x = (2 * i < (int) a.size() ? a[2 * i] : 0);
    int y = (2 * i + 1 < (int) a.size() ? a[2 * i + 1] : 0);
    fa[i] = num(x, y);
  }
  fft(fa, sz >> 1);
  num r(1.0 / (sz >> 1), 0.0);
  for (int i = 0; i <= (sz >> 2); i++) {
    int j = ((sz >> 1) - i) & ((sz >> 1) - 1);
    num fe = (fa[i] + conj(fa[j])) * num(0.5, 0);
    num fo = (fa[i] - conj(fa[j])) * num(0, -0.5);
    num aux = fe * fe + fo * fo * roots[(sz >> 1) + i] * roots[(sz >> 1) + i];
    num tmp = fe * fo;
    fa[i] = r * (conj(aux) + num(0, 2) * conj(tmp));
    fa[j] = r * (aux + num(0, 2) * tmp);
  }
  fft(fa, sz >> 1);
  vector<int64_t> res(need);
  for (int i = 0; i < need; i++) {
    res[i] = llround(i % 2 == 0 ? fa[i >> 1].x : fa[i >> 1].y);
  }
  return res;
}

vector<int64_t> multiply(const vector<int>& a, const vector<int>& b) {
  if (a.empty() || b.empty()) {
    return {};
  }
  if (a == b) {
    return square(a);
  }
  int need = (int) a.size() + (int) b.size() - 1;
  int nbase = 1;
  while ((1 << nbase) < need) nbase++;
  ensure_base(nbase);
  int sz = 1 << nbase;
  if (sz > (int) fa.size()) {
    fa.resize(sz);
  }
  for (int i = 0; i < sz; i++) {
    int x = (i < (int) a.size() ? a[i] : 0);
    int y = (i < (int) b.size() ? b[i] : 0);
    fa[i] = num(x, y);
  }
  fft(fa, sz);
  num r(0, -0.25 / (sz >> 1));
  for (int i = 0; i <= (sz >> 1); i++) {
    int j = (sz - i) & (sz - 1);
    num z = (fa[j] * fa[j] - conj(fa[i] * fa[i])) * r;
    fa[j] = (fa[i] * fa[i] - conj(fa[j] * fa[j])) * r;
    fa[i] = z;
  }
  for (int i = 0; i < (sz >> 1); i++) {
    num A0 = (fa[i] + fa[i + (sz >> 1)]) * num(0.5, 0);
    num A1 = (fa[i] - fa[i + (sz >> 1)]) * num(0.5, 0) * roots[(sz >> 1) + i];
    fa[i] = A0 + A1 * num(0, 1);
  }
  fft(fa, sz >> 1);
  vector<int64_t> res(need);
  for (int i = 0; i < need; i++) {
    res[i] = llround(i % 2 == 0 ? fa[i >> 1].x : fa[i >> 1].y);
  }
  return res;
}
}

int eval(char c) {
    if (c == '?') {
        return 0;
    }
    if (c == 'o') {
        return 1;
    }
    if (c == 'k') {
        return -1;
    }
    throw;
}

const int maxn = 1e6;
#define ll long long

ll dp[maxn];
int val[maxn];
int cnto[maxn], cntk[maxn];

void upmax(ll& x, ll y) {
    x = max(x, y);
}

int main() {
    // freopen("input.txt", "r", stdin);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    // srand(time(0));

    int o, k;
    cin >> o >> k;

    string s, p;
    cin >> s >> p;

    int n = s.size(), m = p.size();
    vector<int> a, b;
    a.resize(n);
    b.resize(m);

    for (int i = 0; i < n; i++) {
        a[n - i - 1] = eval(s[i]);
        cnto[i + 1] = cnto[i] + (s[i] == 'o');
        cntk[i + 1] = cntk[i] + (s[i] == 'k');
    }

    int cnt0 = 0;
    for (int i = 0; i < m; i++) {
        b[i] = eval(p[i]);
        cnt0 += b[i] == 0;
    }

    // for (int i = 0; i < n; i++) {
    //     cout << a[i] << ' ';
    // }
    // cout << endl;

    // for (int i = 0; i < m; i++) {
    //     cout << b[i] << ' ';
    // }
    auto c = fft::multiply(a, b);
    // cout << c[7];
    // return 0;

    for (int i = 0; i + m <= n; i++) {
        if (n - i - 1 >= c.size()) {
            throw;
        }
        // cout << i + n - 1 << ' ' << c[n - i - 1] << endl;
        int x = c[n - i - 1];
        int q = cnt0;
        val[i] = m - cnt0 - (x + m + cnt0) / 2;
        // cout << x << ' ' << q << ' ' << m << endl;
        // int y = x - m + q;

        // assert(y % 2 == 0);
        // val[i] = m - q - y / 2;
        // cout << val[i] << endl;
    }

    for (int i = 0; i < n; i++) {
        if (i + m <= n) {
            long long kek = 1ll * o * (cnto[i + m] - cnto[i]) + 1ll * k * (cntk[i + m] - cntk[i]);
            for (int j = 0; j < val[i] && kek > 0; j++) {
                kek /= 2;
            }
            upmax(dp[i + m], dp[i] + kek);
        }
        upmax(dp[i + 1], dp[i]);
    }

    cout << dp[n];
}