#include <bits/stdc++.h>
using namespace std;
const int N = 5 * 100005;
int sum[N];
char str[5 * 100005];
int costf[5 * 100005];
int costb[5 * 100005];
int n, a, b, t;
int main() {
  scanf("%d", &n);
  scanf("%d", &a);
  scanf("%d", &b);
  scanf("%d", &t);
  cin >> str;
  if (str[0] == 'h')
    costf[1] = 1;
  else
    costf[1] = 1 + b;
  for (int i = 2; i <= n; i++) {
    if (str[i - 1] == 'h')
      costf[i] = (costf[i - 1] + 1 + a);
    else
      costf[i] = (costf[i - 1] + 1 + a + b);
  }
  if (str[n - 1] == 'h')
    costb[n] = 1;
  else
    costb[n] = (1 + b);
  for (int i = n - 1; i >= 1; i--) {
    if (str[i - 1] == 'h')
      costb[i] = (costb[i + 1] + 1 + a);
    else
      costb[i] = (costb[i + 1] + 1 + a + b);
  }
  vector<int> v;
  for (int i = n; i >= 1; i--) {
    v.push_back(costb[i]);
  }
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    int x = t;
    if (costf[i] > x) {
      break;
    } else {
      int temp = 0;
      temp += i;
      x -= costf[i];
      x -= (a * i);
      if (x > 0) temp += (upper_bound(v.begin(), v.end(), x) - v.begin());
      if (temp > n) temp = n;
      ans = max(ans, temp);
    }
  }
  vector<int> vv;
  for (int i = 2; i <= n; i++) {
    vv.push_back(costf[i] - a - costf[1]);
  }
  for (int i = n; i >= 1; i--) {
    int x = t;
    if (costb[i] + costf[1] + a > x)
      break;
    else {
      int temp = 0;
      temp += (n - i + 1);
      temp += 1;
      x -= (costb[i] + a + costf[1]);
      x -= (n - i + 2) * a;
      if (x > 0) temp += (upper_bound(vv.begin(), vv.end(), x) - vv.begin());
      if (temp > n) temp = n;
      ans = max(ans, temp);
    }
  }
  cout << ans;
  return 0;
}
