#include <bits/stdc++.h>
using namespace std;
const int maxn = 500005, INF = 0x3f3f3f3f;
int ta, tb, n, T;
long long t[maxn], t1[maxn];
int main(void) {
  cin >> n >> ta >> tb >> T;
  string s;
  char a;
  cin >> a;
  if (a == 'w') T -= tb;
  T--;
  if (T < 0) {
    cout << 0 << endl;
    return 0;
  }
  cin >> s;
  for (int i = 0; i < n - 1; i++) {
    t[i] = t[i - 1] + 1 + ta;
    if (s[i] == 'w') t[i] += tb;
  }
  reverse(s.begin(), s.end());
  for (int i = 0; i < n - 1; i++) {
    t1[i] = t1[i - 1] + 1 + ta;
    if (s[i] == 'w') t1[i] += tb;
  }
  int res = 0;
  for (int i = 0; i < n; i++) {
    if (t1[i - 1] > T) break;
    int l = 0, r = n - i;
    while (l < r - 1) {
      int mid = (l + r) / 2;
      if (mid > 0 && t1[i - 1] + t[mid - 1] + i * ta <= T)
        l = mid;
      else
        r = mid;
    }
    res = max(res, l + i);
  }
  for (int i = 0; i < n; i++) {
    if (t[i - 1] > T) break;
    int l = 0, r = n - i;
    while (l < r - 1) {
      int mid = (l + r) / 2;
      if (mid > 0 && t[i - 1] + t1[mid - 1] + i * ta <= T)
        l = mid;
      else
        r = mid;
    }
    res = max(res, l + i);
  }
  cout << res + 1 << endl;
  return 0;
}
