#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, b, T, i, j, temp, le, ri, mid, ma = 0;
  cin >> n >> a >> b >> T;
  char str[n];
  cin >> str;
  int r[n], l[n];
  if (str[0] == 'h')
    r[0] = 1;
  else
    r[0] = b + 1;
  for (i = 1; i < n; i++) {
    if (str[i] == 'h')
      r[i] = r[i - 1] + a + 1;
    else
      r[i] = r[i - 1] + a + b + 1;
  }
  if (str[n - 1] == 'h')
    l[0] = a + 1;
  else
    l[0] = a + b + 1;
  for (i = 1; i < n - 1; i++) {
    if (str[n - 1 - i] == 'h')
      l[i] = l[i - 1] + a + 1;
    else
      l[i] = l[i - 1] + a + b + 1;
  }
  for (i = 0; i < n; i++)
    if (r[i] <= T) ma = max(ma, i + 1);
  for (i = 0; i < n - 1; i++) {
    temp = l[i];
    if (temp >= T) continue;
    le = 0;
    ri = n - 1 - i - 1;
    while (ri - le > 1) {
      mid = (le + ri) / 2;
      temp = l[i] + min(i + 1, mid) * a;
      if (temp + r[mid] < T)
        le = mid;
      else
        ri = mid;
    }
    if (l[i] + r[le] + min(i + 1, le) * a <= T) ma = max(ma, i + le + 2);
    if (l[i] + r[ri] + min(i + 1, ri) * a <= T) ma = max(ma, i + ri + 2);
  }
  cout << ma;
}
