#include <bits/stdc++.h>
using namespace std;
inline int read() {
  int x = 0;
  char ch = getchar();
  bool positive = 1;
  for (; ch < '0' || ch > '9'; ch = getchar())
    if (ch == '-') positive = 0;
  for (; ch >= '0' && ch <= '9'; ch = getchar()) x = x * 10 + ch - '0';
  return positive ? x : -x;
}
inline char RC() {
  char c = getchar();
  while (c == ' ' || c == '\n') c = getchar();
  return c;
}
inline long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
inline long long lcm(long long a, long long b, long long MOD) {
  return a / gcd(a, b) * b % MOD;
}
inline long long Sub(long long x, long long y, long long mod) {
  long long res = x - y;
  while (res < 0) res += mod;
  return res;
}
inline long long Add(long long x, long long y, long long mod) {
  long long res = x + y;
  while (res >= mod) res -= mod;
  return res;
}
inline long long POW_MOD(long long x, long long y, long long mod) {
  long long ret = 1;
  while (y > 0) {
    if (y & 1) ret = ret * x % mod;
    x = x * x % mod;
    y >>= 1;
  }
  return ret;
}
const int N = 500005 + 100;
const int M = 400000 + 100;
const long long INF = 9e18;
const int inf = 0x7fffffff;
const long long MOD = 1000000007;
const double PI = acos(-1.0);
const double G = 9.8;
const double eps = 1e-3;
string circle;
int n, a, b, T;
int L[N], R[N];
int find(int l, int r, int rightDis) {
  while (l <= r) {
    int mid = (l + r) >> 1;
    long long expense = L[mid] + R[rightDis];
    int leftDis = n - mid;
    expense += (long long)a * min(leftDis, rightDis);
    if (expense > T) {
      l = mid + 1;
    } else if (expense < T) {
      r = mid - 1;
    } else {
      return mid;
    }
  }
  return l;
}
int main() {
  cin >> n >> a >> b >> T >> circle;
  for (int i = 0; i < circle.size(); ++i) {
    if (i == 0) {
      R[i] = (circle[i] == 'h' ? 0 : b) + 1;
    } else {
      R[i] = R[i - 1] + a + (circle[i] == 'h' ? 0 : b) + 1;
    }
  }
  for (int i = circle.size() - 1; i >= 0; --i) {
    int pre = (i + 1 - n) % n;
    if (pre == 0) {
      L[i] = a + (circle[i] == 'h' ? 0 : b) + 1;
    } else {
      L[i] = L[i + 1] + (circle[i] == 'h' ? 0 : b) + a + 1;
    }
  }
  int ans = 0;
  for (int i = 0; i < n; ++i) {
    if (R[i] > T) break;
    int indx = find(i + 1, n - 1, i);
    ans = max(ans, n - indx + i + 1);
  }
  cout << ans << endl;
  return 0;
}
