#include <bits/stdc++.h>
using namespace std;
const int MOD = (int)1e9 + 7;
const int INF = (int)1e9;
const long long LINF = (long long)1e18;
const long double PI = 2 * acos((long double)0);
const long double EPS = 1e-9;
long long gcd(long long a, long long b) {
  long long r;
  while (b) {
    r = a % b;
    a = b;
    b = r;
  }
  return a;
}
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
long long fpow(long long n, long long k, int p = MOD) {
  long long r = 1;
  for (; k; k >>= 1) {
    if (k & 1) r = r * n % p;
    n = n * n % p;
  }
  return r;
}
template <class T>
void setmin(T& a, T val) {
  if (a > val) a = val;
}
template <class T>
void setmax(T& a, T val) {
  if (a < val) a = val;
}
void addmod(int& a, int val, int p = MOD) {
  if ((a = (a + val)) >= p) a -= p;
}
void submod(int& a, int val, int p = MOD) {
  if ((a = (a - val)) < 0) a += p;
}
int mult(int a, int b, int p = MOD) { return (long long)a * b % p; }
int inv(int a, int p = MOD) { return fpow(a, p - 2, p); }
const int maxn = 500010;
int n, a, b, t;
char s[maxn];
long long pref[maxn];
long long suff[maxn];
int ans = 0;
void go() {
  memset(pref, 0, sizeof(pref));
  memset(suff, 0, sizeof(suff));
  for (int i = (0); i < (n); i++) {
    pref[i] = s[i] == 'h' ? 1 : (b + 1);
    if (i) {
      pref[i] += pref[i - 1] + a;
    }
  }
  for (int i = (n)-1; i >= (0); i--) {
    suff[i] = s[i] == 'h' ? 1 : (b + 1);
    if (i < n - 1) {
      suff[i] += suff[i + 1] + a;
    }
  }
  for (int i = (0); i < (n >> 1); i++) swap(suff[i], suff[n - i - 1]);
  if (t >= pref[n - 1]) ans = n;
  for (int i = (0); i < (n - 1); i++) {
    if (pref[i] > t) break;
    int x = t - pref[i];
    if (x >= (long long)a * (i + 1)) {
      x -= (long long)a * (i + 1);
      int k = upper_bound(suff, suff + n, x) - suff;
      setmax(ans, min(n, i + k + 1));
    } else {
      setmax(ans, i + 1);
    }
  }
}
void solve() {
  scanf("%d%d%d%d%s", &n, &a, &b, &t, s);
  go();
  reverse(s + 1, s + n);
  go();
  cout << ans;
}
int main() {
  solve();
  return 0;
}
