#include <bits/stdc++.h>
using namespace std;
const long long int mod = 1000000007;
const long long int inf = 0x3f3f3f3f3f3f3f3fLL;
const double eps = 1e-9;
const double PI = acos(-1);
long long int i, j, k;
void solve(void);
inline bool equal(double a, double b) { return fabs(a - b) < eps; }
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout << fixed << setprecision(10);
  int t = 1;
  while (t--) solve();
  return 0;
}
void solve() {
  int n, a, b, T;
  cin >> n >> a >> b >> T;
  char c[n];
  for (i = (0); i <= (n - 1); ++i) cin >> c[i];
  int lo = 1, hi = n, mid, ans = 0, left[n], right[n];
  left[0] = right[0] = 1 + (c[0] == 'w' ? b : 0);
  for (i = (1); i <= (n - 1); ++i)
    left[i] = left[i - 1] + a + (c[n - i] == 'w' ? b : 0) + 1;
  for (i = (1); i <= (n - 1); ++i)
    right[i] = right[i - 1] + a + (c[i] == 'w' ? b : 0) + 1;
  while (lo <= hi) {
    mid = (lo + hi) >> 1;
    bool pos = 0;
    for (i = (mid - 1); i >= (0); --i) {
      long long int time1 = right[i] + left[mid - i - 1] - left[0] + i * a;
      if (time1 <= T) pos = 1;
      long long int time2 = left[i] + right[mid - i - 1] - right[0] + i * a;
      if (time2 <= T) pos = 1;
    }
    if (pos) {
      ans = ((ans) > (mid) ? (ans) : (mid));
      lo = mid + 1;
    } else
      hi = mid - 1;
  }
  cout << ans << '\n';
}
