#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  long long n, a, b, t;
  string str;
  cin >> n >> a >> b >> t >> str;
  str += str;
  long long len = 1, l = n, r, remain = t - 1 - (str[n] == 'w') * b, ans = 1;
  if (remain < 0) {
    cout << "0\n";
    return 0;
  }
  while (len < n) {
    long long require = 2 * a + 1 + (str[l - 1] == 'w') * b;
    if (remain < require) {
      break;
    } else {
      l--;
      len++;
      remain -= require;
    }
  }
  for (r = n + 1; r < str.size(); r++) {
    remain -= a + 1 + (str[r] == 'w') * b;
    while (r - l + 1 > n || (l < n && remain < 0)) {
      remain += 2 * a + 1 + (str[l] == 'w') * b;
      l++;
    }
    if (l >= n && remain < 0) break;
    ans = max(ans, r - l + 1);
  }
  len = 1, l = r = n, remain = t - 1 - (str[n] == 'w') * b;
  while (len < n) {
    long long require = 2 * a + 1 + (str[r + 1] == 'w') * b;
    if (remain < require) {
      break;
    } else {
      r++;
      len++;
      remain -= require;
    }
  }
  for (l = n - 1; l > 0; l--) {
    remain -= a + 1 + (str[l] == 'w') * b;
    while (r - l + 1 > n || (r > n && remain < 0)) {
      remain += 2 * a + 1 + (str[r] == 'w') * b;
      r--;
    }
    if (r <= n && remain < 0) break;
    ans = max(ans, r - l + 1);
  }
  cout << ans << '\n';
}
