/*
Keep solving problems.
*/

import java.util.*;
import java.io.*;

public class CFA {
    BufferedReader br;
    PrintWriter out;
    StringTokenizer st;
    boolean eof;
    private static final long MOD = 1000 * 1000 * 1000 + 7;
    private static final int[] dx = {0, -1, 0, 1};
    private static final int[] dy = {1, 0, -1, 0};
    private static final String yes = "Yes";
    private static final String no = "No";

    int n;
    long a;
    long b;
    long T;
    char[] arr;
    void solve() throws IOException {
        n = nextInt();
        a = nextLong();
        b = nextLong();
        T = nextLong();
        arr = nextString().toCharArray();
        int l = 0;
        int h = (int) MOD;
        while (l < h) {
            int mid = (l + h) / 2;
            if (mid > n) {
                h = mid;
                continue;
            }

            if (check(mid)) {
                l = mid + 1;
            }
            else {
                h = mid;
            }
        }

        outln(l - 1);
    }

    boolean check(int mid) {
        if (mid == 0) {
            return true;
        }
        long[] left = findLeft(mid);
        long[] right = findRight(mid);

        long res = Long.MAX_VALUE;
        for (int i = 0; i < mid; i++) {
            long tmp = left[i] + right[mid - 1 - i] - left[0];
            res = Math.min(res, tmp);
        }

        return res <= T;
    }

    long[] findLeft(int mid) {
        long res = 0;
        long[] ret = new long[mid];
        for (int i = 0; i < mid; i++) {
            if (i == 0) {
                if (arr[i] == 'w') {
                    res += b;
                }
                res++;
            }
            else {
                res += a + 1;
                if (arr[n - i] == 'w') {
                    res += b;
                }
            }
            ret[i] = res;
        }

        return ret;
    }

    long[] findRight(int mid) {
        long res = 0;
        long[] ret = new long[mid];
        for (int i = 0; i < mid; i++) {
            if (i == 0) {
                if (arr[i] == 'w') {
                    res += b;
                }
                res++;
            }
            else {
                res += a + 1;
                if (arr[i] == 'w') {
                    res += b;
                }
            }
            ret[i] = res;
        }

        return ret;
    }

    void shuffle(int[] a) {
        int n = a.length;
        for(int i = 0; i < n; i++) {
            int r = i + (int) (Math.random() * (n - i));
            int tmp = a[i];
            a[i] = a[r];
            a[r] = tmp;
        }
    }

    long gcd(long a, long b) {
        while(a != 0 && b != 0) {
            long c = b;
            b = a % b;
            a = c;
        }
        return a + b;
    }

    private void outln(Object o) {
        out.println(o);
    }
    private void out(Object o) {
        out.print(o);
    }
    private void formatPrint(double val) {
        System.out.format("%.9f%n", val);
    }
    public CFA() throws IOException {
        br = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(System.out);
        solve();
        out.close();
    }
    public static void main(String[] args) throws IOException {
        new CFA();
    }

    public long[] nextLongArr(int n) throws IOException{
        long[] res = new long[n];
        for(int i = 0; i < n; i++)
            res[i] = nextLong();
        return res;
    }
    public int[] nextIntArr(int n) throws IOException {
        int[] res = new int[n];
        for(int i = 0; i < n; i++)
            res[i] = nextInt();
        return res;
    }
    public String nextToken() {
        while (st == null || !st.hasMoreTokens()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (Exception e) {
                eof = true;
                return null;
            }
        }
        return st.nextToken();
    }
    public String nextString() {
        try {
            return br.readLine();
        } catch (IOException e) {
            eof = true;
            return null;
        }
    }
    public int nextInt() throws IOException {
        return Integer.parseInt(nextToken());
    }
    public long nextLong() throws IOException {
        return Long.parseLong(nextToken());
    }
    public double nextDouble() throws IOException {
        return Double.parseDouble(nextToken());
    }
}